Condensed Consolidated Statements of Stockholders' Equity (unaudited) - 6 months ended Jun. 30, 2018 - 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		160,424,575	1,052,469	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, net of costs (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		166,658,962	1,045,670	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