Revenue Recognition (Components of Lease Revenue) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Fixed lease revenues	$ 306,319	$ 351,426	$ 955,650	$ 1,159,037
Variable lease revenues	6,429	62,917	56,632	151,844
Total lease revenues	$ 312,748	$ 414,343	$ 1,012,282	$ 1,310,881