SCHEDULE 13G

Amendment No. 3
Perini Corporation
Common Stock
Cusip #713839108


Cusip #713839108
Item 1:	Reporting Person - FMR Corp.
Item 4:	Delaware
Item 5:	532,100
Item 6:	0
Item 7:	532,100
Item 8:	0
Item 9:	532,100
Item 11:	2.011%
Item 12:	    HC


Cusip #713839108
Item 1:	Reporting Person - Edward C. Johnson 3d
Item 4:	United States of America
Item 5:	0
Item 6:	0
Item 7:	532,100
Item 8:	0
Item 9:	532,100
Item 11:	2.011%
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:

		Perini Corporation

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

		73 Mtwayte Avenue
		Framingham, MA  01701-9160


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:

		713839108

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:	532,100

	(b)	Percent of Class:	2.011%

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

	(i)	sole power to vote or to direct
the vote:	532,100

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

	(iii)	sole power to dispose or to
direct the disposition of:	532,100

	(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 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.

	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 statement
is true, complete and correct.

January 10, 2007
Date

/s/Eric D. Roiter
Signature

Eric D, Roiter
Duly authorized under Power of Attorney
dated December 30, 1997 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)



	Pyramis Global Advisors, LLC ("PGALLC"), 53 State
Street, Boston, Massachusetts, 02109, an indirect 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 500,000 shares or 1.890%
of the outstanding Common Stock of Perini Corporation as a
result of its serving as investment adviser to institutional
accounts, non-U.S. mutual funds, or investment companies
registered under Section 8 of the Investment Company Act of
1940 owning such shares.

	Edward C. Johnson 3d and FMR Corp., through its
control of PGALLC, each has sole dispositive power over
500,000 shares and sole power to vote or to direct the voting
of 500,000 shares of Common Stock owned by the
institutional accounts or funds advised by PGALLC as
reported above.

	Pyramis Global Advisors Trust Company ("PGATC"),
53 State Street, Boston, Massachusetts, 02109, an indirect
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 32,100 shares or 0.121% of the
outstanding Common Stock of the Perini Corporation as a
result of its serving as investment manager of institutional
accounts owning such shares.

	Edward C. Johnson 3d and FMR Corp., through its
control of Pyramis Global Advisors Trust Company, each has
sole dispositive power over 32,100 shares and sole power to
vote or to direct the voting of 32,100 shares of Common Stock
owned by the institutional accounts managed by PGATC as
reported above.

	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.



	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, 2007, 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 Perini Corporation at December 31, 2006.

	FMR Corp.

	By /s/ Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney dated
December 30, 1997, by and on behalf of FMR Corp. and its
direct and indirect subsidiaries

	Edward C. Johnson 3d

	By /s/ Eric D. Roiter
	Eric D. Roiter
	Duly authorized under Power of Attorney dated
December 30, 1997, by and on behalf of Edward C. Johnson
3d