Condensed Consolidated Statements of Stockholders' Equity - 3 months ended Mar. 31, 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)				1,916,000	(1,000)
Conversion of operating partnership units and Class B shares to Class A shares	0			$ 19	$ 0	7,811	(21)		7,809	(7,809)
Equity compensation:
LTIP units	3,065									3,065
Restricted stock, net of forfeitures (in shares)				28,000
Restricted stock, net of forfeitures	89					89			89
Dividends and distributions	(31,630)							(16,482)	(16,482)	(14,914)	(234)
Net income	19,145							9,985	9,985	8,926	234
Unrealized gain on valuation of interest rate swap agreements	1,394						736		736	658
Ending balance (in shares) at Mar. 31, 2017		156,689,477	1,095,114	156,689,000	1,095,000
Ending balance at Mar. 31, 2017	$ 1,974,926			$ 1,566	$ 11	$ 1,112,363	$ (2,074)	$ 44,407	$ 1,156,273	$ 810,649	$ 8,004