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, 2014					106,030,000	1,161,000
Beginning 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
Other comprehensive income (loss)	(1,922)			(822)				(822)		(1,100)
Ending balance (in shares) at Dec. 31, 2015					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 Class A shares, net of costs (in shares)					29,610,854
Issuance of Class A shares, net of costs	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
Other comprehensive income (loss)	(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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)					5,659,000	(44,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			23,435	$ 57		23,529	(151)		(23,435)
Equity compensation:
LTIP units	13,632									13,632
Restricted stock, net of forfeitures (in shares)					21,000
Restricted stock, net of forfeitures	468			468			468
Dividends and distributions	(126,963)			(66,789)					(66,789)	(59,238)	(936)
Net income	118,253			62,647					62,647	54,670	936
Other comprehensive income (loss)	(10,516)			(5,615)				(5,615)		(4,901)
Ending balance (in shares) at Dec. 31, 2017		160,424,575	1,052,469		160,425,000	1,052,000
Ending balance at Dec. 31, 2017	$ 1,977,737			$ 1,168,282	$ 1,604	$ 11	$ 1,128,460	$ (8,555)	$ 46,762	$ 801,451	$ 8,004