Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 35,489	$ 32,897	$ 85,993	$ 74,242
Other comprehensive income (loss):
Change in unrealized gain (loss) on valuation of interest rate swap agreements	(1,279)	930	(14,252)	(29,305)
Other comprehensive income (loss)	(1,279)	930	(14,252)	(29,305)
Comprehensive income (loss)	34,210	33,827	71,741	44,937
Net income attributable to non-controlling interests and private perpetual preferred unitholders	(16,683)	(16,924)	(40,618)	(39,752)
Other comprehensive (income) loss attributable to non-controlling interests	586	(979)	6,670	15,561
Comprehensive income (loss) attributable to common stockholders	$ 18,113	$ 15,924	$ 37,793	$ 20,746