Condensed Consolidated Statements of Stockholders' Equity - 9 months ended Sep. 30, 2017 - 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, 2016		154,744,740	1,095,737	154,745,000	1,096,000
Beginning balance at Dec. 31, 2016	$ 1,982,863			$ 1,547	$ 11	$ 1,104,463	$ (2,789)	$ 50,904	$ 1,154,136	$ 820,723	$ 8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				3,577,000	(18,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 36	$ 0	11,087	(54)		11,069	(11,069)
Equity compensation:
LTIP units	10,332									10,332
Restricted stock, net of forfeitures (in shares)				28,000
Restricted stock, net of forfeitures	476					476			476
Dividends and distributions	(95,186)							(49,843)	(49,843)	(44,641)	(702)
Net income	85,993							45,375	45,375	39,916	702
Unrealized gain (loss) on valuation of interest rate swap agreements	(14,252)						(7,582)		(7,582)	(6,670)
Ending balance (in shares) at Sep. 30, 2017		158,349,708	1,077,740	158,350,000	1,078,000
Ending balance at Sep. 30, 2017	$ 1,970,226			$ 1,583	$ 11	$ 1,116,026	$ (10,425)	$ 46,436	$ 1,153,631	$ 808,591	$ 8,004