Leases - Lease Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Interest and Other Income [Abstract]
Fixed income from operating leases	$ 237,607	$ 262,885	$ 474,830	$ 526,240
Variable income from operating leases	63,590	54,955	120,589	108,352
Interest income from direct financing leases	$ 10,190	$ 13,490	$ 23,714	$ 26,756