Condensed Consolidated Statements of Stockholders' Equity (unaudited) - USD ($) $ in Thousands	Total	Class A Common Stock	Class B Common Stock	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Total Stockholders' Equity	Non-controlling Interests	Private Perpetual Preferred Units
Beginning balance (in shares) at Dec. 31, 2017				160,425,000	1,052,000
Beginning balance at Dec. 31, 2017	$ 1,977,737			$ 1,604	$ 11	$ 1,128,460	$ (8,555)	$ 46,762	$ 1,168,282	$ 801,451	$ 8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A shares (in shares)				284,000
Issuance of Class A shares	4,749			$ 3		4,746			4,749
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				7,444,000	(8,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 74	$ (1)	31,605	(18)		31,660	(31,660)
Equity compensation:
LTIP units	13,795									13,795
Restricted stock, net of forfeitures (in shares)				24,000
Restricted stock, net of forfeitures	269					269			269
Dividends and distributions	(95,960)							(52,519)	(52,519)	(42,739)	(702)
Net income	77,472							42,761	42,761	34,009	702
Other comprehensive income (loss)	11,389						6,344		6,344	5,045
Ending balance (in shares) at Sep. 30, 2018				168,177,000	1,044,000
Ending balance at Sep. 30, 2018	1,989,451			$ 1,681	$ 10	1,165,080	(2,229)	37,004	1,201,546	779,901	8,004
Beginning balance (in shares) at Jun. 30, 2018				166,659,000	1,045,000
Beginning balance at Jun. 30, 2018	1,983,141			$ 1,667	$ 10	1,159,162	(4,695)	38,389	1,194,533	780,604	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				1,518,000	(1,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 14		5,765	36		5,815	(5,815)
Equity compensation:
LTIP units	4,700									4,700
Restricted stock, net of forfeitures	153					153			153
Dividends and distributions	(32,084)							(17,727)	(17,727)	(14,123)	(234)
Net income	29,230							16,342	16,342	12,654	234
Other comprehensive income (loss)	4,311						2,430		2,430	1,881
Ending balance (in shares) at Sep. 30, 2018				168,177,000	1,044,000
Ending balance at Sep. 30, 2018	1,989,451			$ 1,681	$ 10	1,165,080	(2,229)	37,004	1,201,546	779,901	8,004
Beginning balance (in shares) at Dec. 31, 2018		173,872,536	1,038,090	173,874,000	1,038,000
Beginning balance at Dec. 31, 2018	1,991,109			$ 1,739	$ 10	1,204,075	(8,853)	41,511	1,238,482	744,623	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				5,204,000	(19,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 52		21,773	(171)		21,654	(21,654)
Equity compensation:
LTIP units	14,971									14,971
Restricted stock, net of forfeitures (in shares)				53,000
Restricted stock, net of forfeitures	421					421			421
Dividends and distributions	(96,370)							(56,098)	(56,098)	(39,570)	(702)
Net income	55,570							32,646	32,646	22,222	702
Other comprehensive income (loss)	(25,355)						(15,086)		(15,086)	(10,269)
Ending balance (in shares) at Sep. 30, 2019		179,131,090	1,018,463	179,131,000	1,019,000
Ending balance at Sep. 30, 2019	1,940,346			$ 1,791	$ 10	1,226,269	(24,110)	18,059	1,222,019	710,323	8,004
Beginning balance (in shares) at Jun. 30, 2019				176,991,000	1,030,000
Beginning balance at Jun. 30, 2019	1,948,032			$ 1,770	$ 10	1,213,170	(20,387)	21,084	1,215,647	724,381	8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				2,141,000	(11,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 21		12,908	(133)		12,796	(12,796)
Equity compensation:
LTIP units	3,456									3,456
Restricted stock, net of forfeitures (in shares)				(1,000)
Restricted stock, net of forfeitures	191					191			191
Dividends and distributions	(32,180)							(18,907)	(18,907)	(13,039)	(234)
Net income	26,784							15,882	15,882	10,668	234
Other comprehensive income (loss)	(5,937)						(3,590)		(3,590)	(2,347)
Ending balance (in shares) at Sep. 30, 2019		179,131,090	1,018,463	179,131,000	1,019,000
Ending balance at Sep. 30, 2019	$ 1,940,346			$ 1,791	$ 10	$ 1,226,269	$ (24,110)	$ 18,059	$ 1,222,019	$ 710,323	$ 8,004