Derivatives (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Stockholders' equity	$ (4,310,800)	$ (4,222,451)	$ (4,310,800)	$ (4,222,451)	$ (4,300,935)	$ (4,331,682)	$ (4,152,887)	$ (4,154,605)
Reclassification to interest expense	(638)	$ (325)	(1,021)	$ (648)
Interest rate cash flow hedge gain (loss) to be reclassified over next 12 months, net	(2,564)		(2,564)
AOCI, cash flow hedges
Derivative [Line Items]
Stockholders' equity	$ 17,724		$ 17,724			$ 11,128