Earnings per Share (Computation of Basic and Diluted Net Income per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Earnings per Share [Abstract]
Net income available to common stockholders - basic	$ 5,889	$ 4,082
Effect of net income attributable to noncontrolling interests	970	955
Net income available to common stockholders - diluted	$ 6,859	$ 5,037
Weighted average shares outstanding-basic	41,292,445	31,294,488
Effect of Class A and Class RS partnership units	6,801,000	7,317,000
Effect of Class O units and options to purchase Class A common stock on an "as if" converted basis	881,000	598,000
Weighted average shares outstanding-diluted	48,973,851	39,209,226
Net income per share attributable to common stockholders - basic	$ 0.14	$ 0.13
Net income per share attributable to common stockholders - diluted	$ 0.14	$ 0.13