SCHEDULE 13G

Amendment No. 0
Amkor Technology Inc
Common Stock
Cusip #031652100


Cusip #031652100
Item 1:	Reporting Person - FMR Corp.
Item 4:	Delaware
Item 5:	19,700
Item 6:	0
Item 7:	19,509,060
Item 8:	0
Item 9:	19,509,060
Item 11:	11.029%
Item 12:	    HC


Cusip #031652100
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	19,509,060
Item 8:	0
Item 9:	19,509,060
Item 11:	11.029%
Item 12:	IN




	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)




Item 1(a).	Name of Issuer:

		Amkor Technology Inc

Item 1(b).	Name of Issuer's Principal Executive Offices:

		1900 South Price Road
		Chandler, AZ  85248


Item 2(a).	Name of Person Filing:

		FMR Corp.

Item 2(b).	Address or Principal Business Office or, if None,
Residence:

		82 Devonshire Street, Boston,
Massachusetts  02109

Item 2(c).	Citizenship:

		Not applicable

Item 2(d).	Title of Class of Securities:

		Common Stock

Item 2(e).	CUSIP Number:

		031652100

Item 3.	This statement is filed pursuant to Rule 13d-1(b) or 13d-2(b)
and the person filing, FMR Corp., is a parent holding company
in accordance with Section 240.13d-1(b)(ii)(G).  (Note:  See
Item 7).

Item 4.	Ownership

	(a)	Amount Beneficially Owned:	19,509,060

	(b)	Percent of Class:	11.029%

	(c)	Number of shares as to which such
person has:

	(i)	sole power to vote or to direct
the vote:	19,700

	(ii)	shared power to vote or to
direct the vote:	0

	(iii)	sole power to dispose or to
direct the disposition of:	19,509,060

	(iv)	shared power to dispose or to
direct the disposition of:	0



Item 5.	Ownership of Five Percent or Less of a Class.

	Not applicable.

Item 6.	Ownership of More than Five Percent on Behalf of Another
Person.

	Various persons have the right to receive or the power to
direct the receipt of dividends from, or the proceeds from the
sale of, the Common Stock of Amkor Technology Inc.  The
interest of one person, Fidelity Leveraged Co Stock Fund, an
investment company registered under the Investment
Company Act of 1940, in the Common Stock of Amkor
Technology Inc, amounted to 9,439,636 shares or 5.337% of
the total outstanding Common Stock at August 31, 2005.

Item 7.	Identification and Classification of the Subsidiary Which
Acquired the Security Being Reported on By the Parent
Holding Company.

	See attached Exhibit A.

Item 8.	Identification and Classification of Members of
the Group.

	Not applicable.  See attached Exhibit A.

Item 9.	Notice of Dissolution of Group.

	Not applicable.

Item 10.	Certification.

	By signing below I certify that, to the best of my knowledge
and belief, the securities referred to above were acquired in the
ordinary course of business and were not acquired for the
purpose of and do not have the effect of changing or
influencing the control of the issuer of such securities and
were not acquired in connection with or as a participant in any
transaction having such purpose or effect.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this statement
is true, complete and correct.

September 12, 2005
Date

/s/Joseph Mari
Signature

Joseph Mari
Duly authorized under Power of Attorney
dated September 9, 2005, by Eric D. Roiter by and on behalf
of FMR Corp. and its direct and indirect subsidiaries


	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)



	Pursuant to the instructions in Item 7 of Schedule 13G,
Fidelity Management & Research Company ("Fidelity"), 82
Devonshire Street, Boston, Massachusetts 02109, a wholly-
owned subsidiary of FMR Corp. and an investment adviser
registered under Section 203 of the Investment Advisers Act
of 1940, is the beneficial owner of 19,489,360 shares or
11.018% of the Common Stock outstanding of Amkor
Technology Inc  ("the Company") as a result of acting as
investment adviser to various investment companies registered
under Section 8 of the Investment Company Act of 1940. The
number of shares of Common Stock of Amkor Technology Inc
owned by the investment companies at August 31, 2005
included 170,910 shares of Common Stock resulting from the
assumed conversion of $9,800,000 principal amount of
AMKOR TECH CONV 5% 3/15/07 (17.4398 shares of
Common Stock for each $1,000 principal amount of
debenture).

	The ownership of one investment company, Fidelity
Leveraged Co Stock Fund, amounted to 9,439,636 shares or
5.337% of the Common Stock outstanding. Fidelity Leveraged
Co Stock Fund has its principal business office at 82
Devonshire Street, Boston, Massachusetts 02109.

	Edward C. Johnson 3d and FMR Corp., through its
control of Fidelity, and the funds each has sole power to
dispose of the 19,489,360 shares owned by the Funds.

	Members of the family of Edward C. Johnson 3d,
Chairman of FMR Corp., are the predominant owners, directly
or through trusts, of Series B shares of common stock of FMR
Corp., representing 49% of the voting power of FMR Corp.
The Johnson family group and all other Series B shareholders
have entered into a shareholders' voting agreement under
which all Series B shares will be voted in accordance with the
majority vote of Series B shares.  Accordingly, through their
ownership of voting common stock and the execution of the
shareholders' voting agreement, members of the Johnson
family may be deemed, under the Investment Company Act of
1940, to form a controlling group with respect to FMR Corp.

	Neither FMR Corp. nor Edward C. Johnson 3d,
Chairman of FMR Corp., has the sole power to vote or direct
the voting of the shares owned directly by the Fidelity Funds,
which power resides with the Funds' Boards of Trustees.
Fidelity carries out the voting of the shares under written
guidelines established by the Funds' Boards of Trustees.

	Fidelity Management Trust Company, 82 Devonshire
Street, Boston, Massachusetts 02109, a wholly-owned
subsidiary of FMR Corp. and a bank as defined in Section
3(a)(6) of the Securities Exchange Act of 1934, is the
beneficial owner of  19,700 shares or 0.011% of the Common
Stock outstanding of the Company as a result of its serving as
investment manager of the institutional account(s).

	Edward C. Johnson 3d and FMR Corp., through its
control of Fidelity Management Trust Company, each has sole
dispositive power over 19,700 shares and sole power to vote
or to direct the voting of 19,700 shares of Common Stock
owned by the institutional account(s) as reported above.



	SCHEDULE 13G - TO BE INCLUDED IN
STATEMENTS
	FILED PURSUANT TO RULE 13d-1(b) or 13d-2(b)
	RULE 13d-1(f)(1)  AGREEMENT

	The undersigned persons, on September 12, 2005,
agree and consent to the joint filing on their behalf of this
Schedule 13G in connection with their beneficial ownership of
the Common Stock of Amkor Technology Inc at August 31,
2005.

	FMR Corp.

	By /s/ Joseph Mari
	Joseph Mari
	Duly authorized under Power of Attorney dated
September 9, 2005, by Eric D. Roiter by and on behalf of
FMR Corp. and its direct and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Joseph Mari
	Joseph Mari
	Duly authorized under Power of Attorney dated
September 9, 2005, by Eric D. Roiter by and on behalf of
Edward C. Johnson 3d

	Fidelity Management & Research Company

	By /s/ Joseph Mari
	Joseph Mari
	Duly authorized under Power of Attorney dated
September 9, 2005, by Eric D. Roiter Secretary

	Fidelity Leveraged Co Stock Fund

	By /s/ Joseph Mari
	Joseph Mari
	Duly authorized under Power of Attorney dated
September 9, 2005, by Eric D. Roiter Secretary