Condensed Consolidated Statements of Stockholders' Equity - 6 months ended Jun. 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)				2,719,000	(15,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 27	$ 0	9,134	(17)		9,144	(9,144)
Equity compensation:
LTIP units	6,673									6,673
Restricted stock, net of forfeitures (in shares)				29,000
Restricted stock, net of forfeitures	294					294			294
Dividends and distributions	(63,408)							(33,118)	(33,118)	(29,822)	(468)
Net income	50,504							26,569	26,569	23,467	468
Unrealized gain (loss) on valuation of interest rate swap agreements	(12,973)						(6,889)		(6,889)	(6,084)
Ending balance (in shares) at Jun. 30, 2017		157,493,025	1,080,475	157,493,000	1,081,000
Ending balance at Jun. 30, 2017	$ 1,963,953			$ 1,574	$ 11	$ 1,113,891	$ (9,695)	$ 44,355	$ 1,150,136	$ 805,813	$ 8,004