Debt - Additional Information (Detail) (USD $)	9 Months Ended	12 Months Ended				9 Months Ended	3 Months Ended	1 Months Ended				1 Months Ended				1 Months Ended
	Sep. 30, 2012	Dec. 31, 2011	Feb. 10, 2012	Sep. 30, 2012 Maximum	Sep. 30, 2012 Minimum	Sep. 30, 2012 License agreement	Sep. 30, 2012 Amendment	Sep. 11, 2012 Amendment Maximum	Sep. 11, 2012 Amendment When taken together with all non-guarantor subsidiaries acquired after September 11, 2012	Sep. 30, 2012 Parent Company and Domestic Subsidiaries	Sep. 30, 2012 Foreign Subsidiaries	Sep. 21, 2012 Revolving Credit Facility	Feb. 10, 2012 Revolving Credit Facility	Nov. 10, 2011 Revolving Credit Facility	Sep. 30, 2012 Revolving Credit Facility Maximum	Feb. 10, 2012 Term Credit Facility	Nov. 10, 2011 Term Credit Facility
Debt Instrument [Line Items]
Credit facilities, maximum borrowing capacity														$ 250,000,000			$ 200,000,000
Credit facilities, maturity														5 years			5 years
Unused borrowings															56,000,000
Note payable under credit facility	194,000,000	75,000,000	370,000,000											75,000,000
Additional borrowing under credit facility												24,000,000	95,000,000			200,000,000
Debt issuance costs			12,300,000
Payment of debt issuance cost	1,094,000	11,800,000
Credit facility, interest rate description	The applicable margin for borrowings under the Revolving Credit Facility is, based on the calculation of the applicable consolidated total leverage ratio, between 0.50% to 1.50% with respect to base rate borrowings and between 1.50% and 2.50% with respect to LIBOR based borrowings. Interest is due and payable monthly. The interest rate in effect at September 30, 2012 was 2.22%.
Credit facility, interest rate margin above federal fund rate	0.50%
Credit facility, interest rate margin above one-month LIBOR rate	1.00%
Credit facility, interest rate margin above base rate				1.50%	0.50%
Credit facility, interest rate margin above LIBOR rate				2.50%	1.50%
Credit facility, borrowing rate	2.22%
Capital stock permitted to purchase, redeem or retire, shares								2,500,000
Acquisition of non-guarantor subsidiaries, permitted amount								75,000,000	200,000,000
Payment of additional financing costs							500,000
Repayment of term portion of credit agreement	9,375,000
Percentage of capital stock pledged as collateral										100.00%	65.00%
Financed internally used software						14,800,000
License agreement period						5 years
Accrued and other current liabilities						2,900,000
Other non current liabilities						$ 9,300,000
Annual payments due date						April through 2016