Accumulated Other Comprehensive Income (Summary of Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period		$ 3,671,903	$ 3,739,703	$ 3,715,023	$ 3,332,988
Other comprehensive income (loss) before reclassifications		(201)	1,037	2,046	(35,211)
(Gain) loss reclassified from accumulated other comprehensive loss to net income		3,172	4,309	9,186	8,818
Share of investee's other comprehensive income	[1]	1,508	0	4,083	0
Derecognition of interest rate swap			12,934		12,934
Net current-period other comprehensive income		4,479	18,280	15,315	(13,459)
Balance at the end of the period		3,682,584	3,713,662	3,682,584	3,713,662
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period		(27,754)	(61,111)	(38,590)	(29,372)
Share of investee's other comprehensive income		1,508		4,083
Balance at the end of the period		$ (23,275)	$ (42,831)	$ (23,275)	$ (42,831)

[1] The amount for 2021 is shown net of deferred tax expense of $0.4 million for the three months ended September 30, 2021, and $1.2 million for the nine months ended September 30, 2021.