Land, Buildings and Improvements and Assets Held for Sale - Operating Lease Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Operating Lease, Lease Income [Abstract]
Lease income — fixed	$ 236,997	$ 222,057	$ 475,965	$ 437,175
Lease income – variable	24,472	22,277	47,552	43,539
Total operating lease income	$ 261,469	$ 244,334	$ 523,517	$ 480,714