Condensed Consolidated Statements of Stockholders' Equity - 6 months ended Jun. 30, 2016 - 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, 2015		118,903,312	1,120,067	118,903,000	1,120,000
Beginning balance at Dec. 31, 2015	$ 1,372,686			$ 1,189	$ 11	$ 469,152	$ (883)	$ 55,260	$ 524,729	$ 839,953	$ 8,004
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of operating partnership units and Class B shares to Class A shares (in shares)				3,858,000	(20,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 38	$ 0	15,201	(166)		15,073	(15,073)
Equity compensation:
LTIP units	4,421									4,421
Restricted stock, net of forfeitures (in shares)				20,000
Restricted stock, net of forfeitures	225					225			225
Dividends and distributions	(51,673)							(23,253)	(23,253)	(27,952)	(468)
Net income	41,345							18,517	18,517	22,360	468
Unrealized loss on valuation of interest rate swap agreements	(30,235)						(13,695)		(13,695)	(16,540)
Ending balance (in shares) at Jun. 30, 2016		122,781,134	1,100,089	122,781,000	1,100,000
Ending balance at Jun. 30, 2016	$ 1,336,769			$ 1,227	$ 11	$ 484,578	$ (14,744)	$ 50,524	$ 521,596	$ 807,169	$ 8,004