SCHEDULE 13G

Amendment No. 3
webMethods Incorporated
Common Stock
Cusip #94768C108


Cusip #94768C108
Item 1:	Reporting Person - FMR Corp.
Item 4:	Delaware
Item 5:	0
Item 6:	0
Item 7:	1,049,700
Item 8:	0
Item 9:	1,049,700
Item 11:	2.054%
Item 12:	    HC


Cusip #94768C108
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	1,049,700
Item 8:	0
Item 9:	1,049,700
Item 11:	2.054%
Item 12:	IN


Cusip #94768C108
Item 1:	Reporting Person - Abigail P. Johnson
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	1,049,700
Item 8:	0
Item 9:	1,049,700
Item 11:	2.054%
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:

		webMethods Incorporated

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

		3930 Pender Drive
		Fairfax, VA  22030

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:

		94768C108

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:	1,049,700

	(b)	Percent of Class:	2.054%

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

	(i)	sole power to vote or to direct
the vote:	0

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

	(iii)	sole power to dispose or to
direct the disposition of:	1,049,700

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



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

	If this statement is being filed to report the fact that as of the
date hereof, the reporting person has ceased to be the
beneficial owner of more than five percent of the class of
securities, check the following (X).

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

	Not applicable

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

	See attached Exhibit(s) A, B.

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.

	Inasmuch as the reporting persons are no longer the beneficial
owners of more than five percent of the number of shares
outstanding, the reporting persons have no further reporting
obligation under Section 13(d) of the Securities and Exchange
Commission thereunder, and the reporting persons have no
obligation to amend this Statement if any material change
occurs in the facts set forth herein.

Signature

	After reasonable inquiry and to the best of my knowledge and
belief, I certify that the information set forth in this Schedule
13G in connection with FMR Corp.'s beneficial ownership of
the Common Stock of webMethods Incorporated at December
31, 2002 is true, complete and correct.

January 10, 2003
Date

/s/Lena G. Goldberg
Signature

Lena G. Goldberg
Duly authorized under Power of Attorney
dated January 3, 2003 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
1,049,700 shares or 2.054% of the Common Stock
outstanding of webMethods Incorporated  ("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.

	Edward C. Johnson 3d, FMR Corp., through its
control of Fidelity, and the funds each has sole power to
dispose of the 1,049,700 shares owned by the Funds.

	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.

	Members of the Edward C. Johnson 3d family are the
predominant owners of Class B shares of common stock of
FMR Corp., representing approximately 49% of the voting
power of FMR Corp.  Mr. Johnson 3d owns 12.0% and
Abigail Johnson owns 24.5% of the aggregate outstanding
voting stock of FMR Corp.  Mr. Johnson 3d is Chairman of
FMR Corp. and Abigail P. Johnson is a Director of FMR
Corp.  The Johnson family group and all other Class B
shareholders have entered into a shareholders' voting
agreement under which all Class B shares will be voted in
accordance with the majority vote of Class 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.




	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 January 10, 2003, 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 webMethods Incorporated at December 31,
2002.

	FMR Corp.

	By /s/ Lena G. Goldberg
	Lena G. Goldberg
	Duly authorized under Power of Attorney
	dated January 3, 2003, by and on behalf
	of FMR Corp. and its direct and indirect
	subsidiaries

	Edward C. Johnson 3d

	By /s/ Lena G. Goldberg
	Lena G. Goldberg
	Duly authorized under Power of Attorney
	dated January 3, 2003, by and on behalf
	of Edward C. Johnson 3d

	Abigail P. Johnson

	By /s/ Lena G. Goldberg
	Lena G. Goldberg
	Duly authorized under Power of Attorney
	dated January 3, 2003, by and on behalf
	of Abigail P. Johnson

	Fidelity Management & Research Company

	By /s/ Lena G. Goldberg
	Lena G. Goldberg
	Senior V.P. and General Counsel. FMR Corp.