Accumulated Other Comprehensive Loss (Summary of Changes in Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	$ 3,739,703	$ 3,351,767	$ 3,332,988	$ 3,238,126
Other comprehensive income (loss) before reclassifications	1,802	(6,406)	(32,999)	(25,311)
Reclassifications	4,121	199	8,441	(21)
Terminated swap amortization	(577)	(764)	(1,835)	(2,055)
Net current-period other comprehensive income (loss)	18,280	(6,971)	(13,459)	(27,387)
Balance at the end of the period	3,713,662	3,380,056	3,713,662	3,380,056
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Balance at the beginning of the period	(61,111)	(28,542)	(29,372)	(8,126)
Terminated swap amortization	(577)	(764)	(1,835)	(2,055)
Balance at the end of the period	(42,831)	$ (35,513)	$ (42,831)	$ (35,513)
Interest rate swap
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Derecognition of interest rate swap	$ 12,934