Earnings per Share (Computation of Basic and Diluted Net Income per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings per Share [Abstract]
Net income available to common stockholders - basic		$ 5,100	$ 4,632	$ 10,989	$ 8,714
Effect of net income attributable to noncontrolling interests		707	888	1,677	1,843
Net income available to common stockholders - diluted		$ 5,807	$ 5,520	$ 12,666	$ 10,557
Weighted average shares outstanding-basic		47,783,093	36,668,755	44,537,769	33,996,467
Effect of Class A and Class RS partnership units		6,794,000	7,063,000	6,797,000	7,189,000
Effect of Class O units and options to purchase Class A common stock on an "as if" converted basis	[1]	998,000	712,000	939,000	683,000
Weighted average shares outstanding-diluted		55,574,545	44,444,104	52,274,198	41,867,944
Net income per share attributable to common stockholders - basic		$ 0.11	$ 0.13	$ 0.25	$ 0.26
Net income per share attributable to common stockholders - diluted		$ 0.10	$ 0.12	$ 0.24	$ 0.25

[1] The Class A units, Class RS units and Class O units represent limited partnership interests in the Operating Partnership, and are described in more detail in Note 7.