Long-Term Debt Activity - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified			3 Months Ended		3 Months Ended			3 Months Ended			3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 5.125% senior notes due 2022	Dec. 18, 2012 5.125% senior notes due 2022	Mar. 31, 2013 Amended Senior Secured Credit Facility	Mar. 31, 2013 Term Loan Credit Facilty Amended Senior Secured Credit Facility	Dec. 18, 2012 Term Loan Credit Facilty Amended Senior Secured Credit Facility	Mar. 31, 2013 Term Loan Credit Facilty Amended Senior Secured Credit Facility Quarterly Principle Payment	Mar. 31, 2013 Term Loan Credit Facilty Amended Senior Secured Credit Facility Quarterly Principle Payment Maximum	Dec. 18, 2012 Term Loan Credit Facilty Amended Senior Secured Credit Facility Remaining principal due on December 18, 2019	Mar. 31, 2013 Revolving Credit Line Amended Senior Secured Credit Facility	Dec. 18, 2012 Revolving Credit Line Amended Senior Secured Credit Facility
Debt Instrument [Line Items]
Aggregate principal amount issued				$ 400,000			$ 700,000			$ 652,750		$ 100,000
Maturity period						7 years					5 years
Quarterly principal payments due								1,750
Maturity date						2019-12			2019-09		2017-12
Debt instrument, maturity date			Dec. 15, 2022		Dec. 18, 2019
Maturity year			2022
Interest rate				5.125%
Carrying value of long-term debt	1,761,784	1,764,010
Fair value of long-term debt	$ 1,849,446	$ 1,851,246