Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 30,184	$ 31,359	$ 48,242	$ 50,504
Other comprehensive income (loss):
Unrealized gain (loss) on valuation of interest rate swap agreements	1,763	(14,410)	5,943	(13,016)
Less: amount reclassified into interest expense	536	43	1,135	43
Other comprehensive income (loss)	2,299	(14,367)	7,078	(12,973)
Comprehensive income (loss)	32,483	16,992	55,320	37,531
Net income attributable to non-controlling interests and private perpetual preferred unitholders	(13,533)	(14,775)	(21,823)	(23,935)
Other comprehensive (income) loss attributable to non-controlling interests	(1,004)	6,742	(3,164)	6,084
Comprehensive income (loss) attributable to common stockholders	$ 17,946	$ 8,959	$ 30,333	$ 19,680