Issuance of Notes Payable and Warrants - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	1 Months Ended	3 Months Ended			3 Months Ended		1 Months Ended
	Aug. 21, 2008	Mar. 31, 2013	Mar. 31, 2013 Class A	Dec. 31, 2012 Class A	Mar. 31, 2013 Class A Maximum	Mar. 31, 2013 Senior Notes	Aug. 21, 2008 Warrant Class A
Issuance Of Notes Payable And Warrants [Line Items]
Principal amount of senior notes	$ 120,000
Principal amount of senior notes due, year	2020
Senior Notes coupon interest	5.20%
Number of Class A Shares purchased, warrants							5,455
Class A Shares purchase price per share							$ 22.00
Class A Common stock par value			$ 0.01	$ 0.01			$ 0.01
Senior notes effective yield		7.94%
Event of default under the indenture accreted amount due and payable, percentage						33.33%
Maximum percent of aggregate principal amount of senior notes owned by holder or group of affiliates for transfer		15.00%
Maximum percent of voting securities and total shares of class A common stock owned by holder or group of affiliates for warrant transfer		2.00%
Percent of outstanding shares of common stock owned by holder or group of affiliates for warrant transfer					25.00%