Quarterly Results of Operations - Summary of Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Net revenue	$ 65,262	$ 62,274	$ 61,846	$ 52,656	$ 60,093	$ 57,786	$ 56,950	$ 49,087	$ 242,038	$ 223,916	$ 223,253
Net income (loss) applicable to common stockholders	$ 5,942	$ 8,057	$ 8,735	$ 4,388	$ 151,093	$ (21,384)	$ 5,073	$ (957)	$ 27,122	$ 133,825	$ 13,601
Net income (loss) per share, basic	$ 0.07	$ 0.09	$ 0.10	$ 0.05	$ 1.72	$ (0.24)	$ 0.06	$ (0.01)	$ 0.31	$ 1.53	$ 0.16
Net income (loss) per share, diluted	$ 0.07	$ 0.09	$ 0.10	$ 0.05	$ 1.67	$ (0.24)	$ 0.06	$ (0.01)	$ 0.30	$ 1.50	$ 0.16