Combined Guarantor Subsidiaries - Leases - Components of Rental Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Rental revenues:
Fixed lease payments	$ 149,582	$ 166,927	$ 460,584	$ 513,356
Variable lease payments	31,034	33,384	96,405	107,252
Total rental revenues	180,616	200,311	556,989	620,608
Guarantor Subsidiaries
Rental revenues:
Fixed lease payments	56,501	65,031	171,564	195,249
Variable lease payments	10,994	12,036	34,519	37,500
Total rental revenues	$ 67,495	$ 77,067	$ 206,083	$ 232,749