Derivatives (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Stockholders' equity	$ (4,260,143)	$ (4,287,209)	$ (4,260,143)	$ (4,287,209)	$ (4,270,878)	$ (4,319,304)	$ (4,310,800)	$ (4,331,682)
Gain (loss) reclassification to interest expense	565	642	2,494	1,663
Interest rate cash flow hedge gain (loss) to be reclassified over next 12 months, net	2,349,000		2,349,000
AOCI, cash flow hedges
Derivative [Line Items]
Stockholders' equity	15,535		15,535			16,445
Accumulated Other Comprehensive Income (Loss)
Derivative [Line Items]
Stockholders' equity	15,535	17,082	15,535	17,082	$ 14,516	$ 16,445	$ 17,724	$ 11,128
Gain (loss) reclassification to interest expense	$ 565	$ 642	$ 2,494	$ 1,663