Condensed Consolidated Statements of Stockholders' Equity (unaudited) - 3 months ended Mar. 31, 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]
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		163,321,049	1,048,161	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