Derivatives (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Stockholders' equity	$ (4,287,209)	$ (4,626,504)	$ (4,287,209)	$ (4,626,504)	$ (4,310,800)	$ (4,331,682)	$ (4,222,451)	$ (4,154,605)
Reclassification to interest expense	(642)	$ (327)	(1,663)	$ (975)
Interest rate cash flow hedge gain (loss) to be reclassified over next 12 months, net	(2,574)		(2,574)
AOCI, cash flow hedges
Derivative [Line Items]
Stockholders' equity	$ 17,082		$ 17,082			$ 11,128