Subsequent Event - Additional Information (Detail) (USD $)	9 Months Ended			1 Months Ended		1 Months Ended						1 Months Ended					1 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Revolving Credit Facilities	Oct. 31, 2012 Refinancing of Debt	Oct. 26, 2012 Refinancing of Debt	Oct. 31, 2012 Refinancing of Debt Wholly Owned Subsidiary Minimum	Oct. 31, 2012 Refinancing of Debt Subsidiaries Minimum	Oct. 31, 2012 Refinancing of Debt Term Loan	Oct. 26, 2012 Refinancing of Debt Term Loan Installment	Oct. 26, 2012 Refinancing of Debt Swing Line Loan	Oct. 26, 2012 Refinancing of Debt Letter of Credit	Oct. 31, 2012 Refinancing of Debt Revolving Credit Facilities	Oct. 31, 2012 Refinancing of Debt Base Rate Minimum	Oct. 31, 2012 Refinancing of Debt Base Rate Maximum	Oct. 31, 2012 Refinancing of Debt Euro Dollar Rate Minimum	Oct. 31, 2012 Refinancing of Debt Euro Dollar Rate Maximum	Oct. 31, 2012 Amendment and Waiver to Note Purchase Agreement	Oct. 31, 2012 Amendment and Waiver to Note Purchase Agreement Wholly Owned Subsidiary Minimum	Oct. 31, 2012 Amendment and Waiver to Note Purchase Agreement Subsidiaries Minimum	Oct. 31, 2012 Amendment and Waiver to Note Purchase Agreement Series A Senior Notes	Oct. 31, 2012 Amendment and Waiver to Note Purchase Agreement Series B Senior Notes	Oct. 31, 2012 Amendment and Waiver to Note Purchase Agreement Series C Senior Notes
Subsequent Event [Line Items]
Credit Facility, maximum borrowing capacity					$ 225,000,000				$ 60,000,000
Amount of Revolving Credit Facility	250,000,000				165,000,000					15,000,000	50,000,000
Credit Facility, maximum additional borrowing capacity					100,000,000
Maturity date			2013-03-26					2017-10-26				2017-10-26
Principal amount of existing term loan paid off	25,489,000	29,674,000		15,000,000
Principal amount of existing senior notes paid off				60,000,000																15,000,000	10,000,000	35,000,000
Debt instrument first installment payment date								Dec. 31, 2012
Debt instrument, number of quarterly installments									20
Debt instrument, quarterly installments amount								3,000,000
Credit Facility, additional interest rate over Federal Funds Rate				0.50%
Credit Facility, additional interest rate over Eurodollar Rate				1.00%
Credit Facility, applicable margin on Base Rate Advances				1.50%
Credit Facility, applicable margin on Eurodollar Rate Advances				2.50%
Credit Facility, interest rate adjustment													1.25%	1.75%	2.25%	2.75%
Percentage of consolidated adjusted EBITDA that guarantor subsidiaries represent.						95.00%	70.00%											95.00%	70.00%
Prepayment fee																	3,600,000
Revolving Credit Facility terminated				$ 250,000,000