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]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				2,870,000	(4,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 29	$ (1)	10,162	(101)		10,089	(10,089)
Equity compensation:
LTIP units	4,577									4,577
Restricted stock, net of forfeitures (in shares)				26,000
Restricted stock, net of forfeitures	(22)					(22)			(22)
Dividends and distributions	(31,791)							(17,207)	(17,207)	(14,350)	(234)
Net income	18,058							9,768	9,768	8,056	234
Other comprehensive income (loss)	4,779						2,619		2,619	2,160
Ending balance (in shares) at Mar. 31, 2018				163,321,000	1,048,000
Ending balance at Mar. 31, 2018	1,973,338			$ 1,633	$ 10	1,138,600	(6,037)	39,323	1,173,529	791,805	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)				1,625,000	(3,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 16		3,271	(5)		3,282	(3,282)
Equity compensation:
LTIP units	5,379									5,379
Restricted stock, net of forfeitures (in shares)				59,000
Restricted stock, net of forfeitures	40					40			40
Dividends and distributions	(31,942)							(18,520)	(18,520)	(13,188)	(234)
Net income	9,856							5,677	5,677	3,945	234
Other comprehensive income (loss)	(7,241)						(4,272)		(4,272)	(2,969)
Ending balance (in shares) at Mar. 31, 2019		175,557,910	1,035,327	175,558,000	1,035,000
Ending balance at Mar. 31, 2019	$ 1,967,201			$ 1,755	$ 10	$ 1,207,386	$ (13,130)	$ 28,668	$ 1,224,689	$ 734,508	$ 8,004