Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Class A [Member]	Common Class B [Member]	Total Stockholders' Equity [Member]	Common Stock [Member] Common Class A [Member]	Common Stock [Member] Common Class B [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	Private Perpetual Preferred Units [Member]
Beginning balance (in shares) at Dec. 31, 2013					94,484,000	1,122,000
Beginning balance at Dec. 31, 2013	$ 1,003,185			$ 385,158	$ 945	$ 11	$ 316,558	$ 0	$ 67,644	$ 618,027	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock (in shares)					2,556,000	110,000
Issuance of Common Stock	379,328			44,398	$ 25	$ 1	44,372			334,930
Redemption of operating partnership units	(829)									(829)
Issuance of private perpetual preferred units in exchange for common units	0									(8,004)	8,004
Equity component of senior unsecured notes	13,204			4,857			4,857			8,347
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					8,995,000	(71,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			40,701	$ 90		40,611			(40,701)
Equity compensation:
LTIP units	3,265									3,265
Restricted stock, net of forfeitures (in shares)					(5,000)
Restricted stock, net of forfeitures	455			455			455
Dividends and distributions	(87,721)			(33,598)					(33,598)	(53,647)	(476)
Net income	70,210			26,667					26,667	43,067	476
Unrealized loss on valuation of interest rate swap agreements	0
Ending balance (in shares) at Dec. 31, 2014					106,030,000	1,161,000
Ending balance at Dec. 31, 2014	1,381,097			468,638	$ 1,060	$ 12	406,853	0	60,713	904,455	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					12,859,000	(41,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			62,070	$ 129	$ (1)	62,003	(61)		(62,070)
Equity compensation:
LTIP units	5,187									5,187
Restricted stock, net of forfeitures (in shares)					14,000
Restricted stock, net of forfeitures	296			296			296
Dividends and distributions	(91,900)			(39,183)					(39,183)	(51,781)	(936)
Net income	79,928			33,730					33,730	45,262	936
Unrealized loss on valuation of interest rate swap agreements	(1,922)			(822)				(822)		(1,100)
Ending balance (in shares) at Dec. 31, 2015		118,903,312	1,120,067		118,903,000	1,120,000
Ending balance at Dec. 31, 2015	1,372,686			524,729	$ 1,189	$ 11	469,152	(883)	55,260	839,953	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Common Stock (in shares)					29,610,854
Issuance of Common Stock	611,206			611,206	$ 296		610,910
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					6,191,000	(24,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			23,678	$ 62	$ 0	24,044	(428)		(23,678)
Equity compensation:
LTIP units	9,372									9,372
Restricted stock, net of forfeitures (in shares)					40,000
Restricted stock, net of forfeitures	357			357			357
Dividends and distributions	(114,954)			(55,812)					(55,812)	(58,206)	(936)
Net income	107,250			51,456					51,456	54,858	936
Unrealized loss on valuation of interest rate swap agreements	(3,054)			(1,478)				(1,478)		(1,576)
Ending balance (in shares) at Dec. 31, 2016		154,744,740	1,095,737		154,745,000	1,096,000
Ending balance at Dec. 31, 2016	$ 1,982,863			$ 1,154,136	$ 1,547	$ 11	$ 1,104,463	$ (2,789)	$ 50,904	$ 820,723	$ 8,004