Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 18,930	$ 30,184	$ 28,786	$ 48,242
Other comprehensive income (loss):
Unrealized gain (loss) on valuation of interest rate swap agreements	(12,346)	1,763	(19,736)	5,943
Less: amount reclassified into interest expense	169	536	318	1,135
Other comprehensive income (loss)	(12,177)	2,299	(19,418)	7,078
Comprehensive income	6,753	32,483	9,368	55,320
Net income attributable to non-controlling interests and private perpetual preferred unitholders	(7,843)	(13,533)	(12,022)	(21,823)
Other comprehensive (income) loss attributable to non-controlling interests	4,953	(1,004)	7,922	(3,164)
Comprehensive income attributable to common stockholders	$ 3,863	$ 17,946	$ 5,268	$ 30,333