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)				5,926,000	(7,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 60	$ (1)	25,840	(54)		25,845	(25,845)
Equity compensation:
LTIP units	9,095									9,095
Restricted stock, net of forfeitures (in shares)				24,000
Restricted stock, net of forfeitures	116					116			116
Dividends and distributions	(63,876)							(34,792)	(34,792)	(28,616)	(468)
Net income	48,242							26,419	26,419	21,355	468
Other comprehensive income (loss)	7,078						3,914		3,914	3,164
Ending balance (in shares) at Jun. 30, 2018				166,659,000	1,045,000
Ending 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
Beginning balance (in shares) at Mar. 31, 2018				163,321,000	1,048,000
Beginning 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
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)				3,056,000	(3,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 31	$ 0	15,678	47		15,756	(15,756)
Equity compensation:
LTIP units	4,518									4,518
Restricted stock, net of forfeitures (in shares)				(2,000)
Restricted stock, net of forfeitures	138					138			138
Dividends and distributions	(32,085)							(17,585)	(17,585)	(14,266)	(234)
Net income	30,184							16,651	16,651	13,299	234
Other comprehensive income (loss)	2,299						1,295		1,295	1,004
Ending balance (in shares) at Jun. 30, 2018				166,659,000	1,045,000
Ending 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
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)				3,063,000	(8,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 31	$ 0	8,865	(38)		8,858	(8,858)
Equity compensation:
LTIP units	11,515									11,515
Restricted stock, net of forfeitures (in shares)				54,000
Restricted stock, net of forfeitures	230					230			230
Dividends and distributions	(64,190)							(37,191)	(37,191)	(26,531)	(468)
Net income	28,786							16,764	16,764	11,554	468
Other comprehensive income (loss)	(19,418)						(11,496)		(11,496)	(7,922)
Ending balance (in shares) at Jun. 30, 2019		176,991,123	1,029,782	176,991,000	1,030,000
Ending 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
Beginning balance (in shares) at Mar. 31, 2019				175,558,000	1,035,000
Beginning 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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				1,438,000	(5,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 15	$ 0	5,594	(33)		5,576	(5,576)
Equity compensation:
LTIP units	6,136									6,136
Restricted stock, net of forfeitures (in shares)				(5,000)
Restricted stock, net of forfeitures	190					190			190
Dividends and distributions	(32,248)							(18,671)	(18,671)	(13,343)	(234)
Net income	18,930							11,087	11,087	7,609	234
Other comprehensive income (loss)	(12,177)						(7,224)		(7,224)	(4,953)
Ending balance (in shares) at Jun. 30, 2019		176,991,123	1,029,782	176,991,000	1,030,000
Ending 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