Derivative Instruments (Narrative) (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2021	Dec. 31, 2020
Derivative [Line Items]
Derivative, Notional Amount		$ 2,977,293	$ 3,015,189
Derivative Asset	[1]	61,358	89,889
Monetized Interest Rate Floor [Member]
Derivative [Line Items]
Derivative, Notional Amount		1,500,000
Derivative Asset		163,200
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimated Net Amount to be Transferred		$ 111,700
Derivative Instruments, Gain (Loss) Reclassification from Accumulated OCI to Income, Estimate of Time to Transfer		5 years 6 months
Interest rate swaps
Derivative [Line Items]
Derivative, Notional Amount		$ 2,270,249	2,367,017
Derivative Asset		59,170	86,389
Variation Margin Impact to Positive Fair Values of Cleared Swaps		(207)	0
Variation Margin Impact to Negative Fair Values of Cleared Swaps		$ (46,600)	$ (69,200)

[1] * The fair value of each class of derivative is shown in Note 11.