Line Of Credit Facility - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	Nov. 30, 2010	Jul. 31, 2011
Line of Credit Facility [Line Items]
Syndicated line of credit, terminated	$ 450.0
Syndicated line of credit, maximum capacity	650.0
Syndicated line of credit, optional maximum capacity at any time prior to the expiration (subject to receipt of commitments for the increased amount from existing and new lenders)	850.0
Syndicated line of credit facility, expiration date	November 30, 2015
Description of amendment to Facility		On June 3, 2011, the Company executed an amendment to the Facility regarding permitted acquisitions. In connection with the amendment, the leverage ratio, both before and after giving effect to an acquisition, cannot be greater than 3.25 to 1 for any acquisition occurring on or prior to June 3, 2012, and 3.10 to 1 for any acquisition occurring thereafter. The Company was in compliance with all covenants as of July 31, 2011.
Line of credit, amount outstanding		365.0
Line of credit, borrowing capacity currently available		183.5
Interest Rate Swap
Line of Credit Facility [Line Items]
Derivative agreement date		Feb. 19, 2009
Description of derivative agreement		Entered into a two-year interest rate swap agreement with an underlying notional amount of $100.0 million, pursuant to which the Company received variable interest payments based on LIBOR and paid fixed interest at a rate of 1.47%. This interest rate swap expired on February 19, 2011.
Notional amount of derivatives		100.0
Derivative, fixed interest rate		1.47%
Derivative expiration date		Feb. 19, 2011
Fair value of derivatives, which was included in retirement plans and other		0.2
Effective portion of cash flow hedges included in accumulated other comprehensive loss, before tax		(0.2)
Effective portion of cash flow hedges included in accumulated other comprehensive loss, net of tax		(0.1)
Forward starting swaps
Line of Credit Facility [Line Items]
Derivative agreement date		Oct. 19, 2010
Description of derivative agreement		Entered into a three-year forward starting interest rate swap agreement with an underlying notional amount of $25.0 million, pursuant to which the Company receives variable interest payments based on LIBOR and pays fixed interest at a rate of 0.89%.
Notional amount of derivatives		$ 25.0
Derivative, fixed interest rate		0.89%
Derivative, effective date		Feb. 24, 2011
Maximum | Acquisition occurring on or prior to june 3, 2012
Line of Credit Facility [Line Items]
Leverage ratio		3.25
Maximum | Acquisition occurring thereafter june 3, 2012
Line of Credit Facility [Line Items]
Leverage ratio		3.10