Selected Quarterly Financial Data (Unaudited) Selected Quarterly Financial Data (Unaudited) (Quarterly Financial Information - 2014) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Selected Quarterly Financial Data [Abstract]
Net revenues	$ 65,027	$ 63,251	$ 61,204	$ 59,018	$ 58,642	$ 58,282	$ 56,313	$ 55,751	$ 248,500	$ 228,988	$ 177,509
Net income attributable to common stockholders	$ 41,188	$ 33,032	$ 44,595	$ 32,725	$ 54,397	$ 33,600	$ 31,182	$ 29,683	$ 151,540	$ 148,862	$ 101,609
Weighted average common shares outstanding:
Basic	39,847,860	39,283,919	38,520,221	38,401,647	37,727,868	37,566,221	37,566,221	37,558,067	39,013,412	37,604,594	33,375,966
Diluted	39,993,445	39,651,900	38,561,384	38,414,791	37,741,162	37,583,141	37,607,117	37,645,265	39,155,380	37,644,171	33,416,014
Basic:
Net income per common share attributable to common stockholders	$ 1.03	$ 0.84	$ 1.16	$ 0.85	$ 1.44	$ 0.89	$ 0.83	$ 0.79	$ 3.88	$ 3.96	$ 3.04
Diluted:
Net income per common share attributable to common stockholders	$ 1.03	$ 0.83	$ 1.16	$ 0.85	$ 1.44	$ 0.89	$ 0.83	$ 0.79	$ 3.87	$ 3.95	$ 3.04