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Investment Securities (Summary of Held-to-Maturity Debt Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Amortized Cost	$ 6,506,047		$ 6,198,339
Unrealized Gains	882		138,254
Unrealized Losses	(856,810)		(55,657)
Fair Value	5,650,119		6,280,936
Allowance	209	$ 210	214	$ 234	$ 382	$ 299
Net Carrying Value	6,505,838		6,198,125
Interest receivable	19,700		21,200
Agency CMO
Schedule of Investments [Line Items]
Amortized Cost	29,854		42,405
Unrealized Gains	0		655
Unrealized Losses	(2,063)		(25)
Fair Value	27,791		43,035
Allowance	0		0
Net Carrying Value	29,854		42,405
Agency MBS
Schedule of Investments [Line Items]
Amortized Cost	2,701,984		2,901,593
Unrealized Gains	674		71,444
Unrealized Losses	(379,332)		(11,788)
Fair Value	2,323,326		2,961,249
Allowance	0		0
Net Carrying Value	2,701,984		2,901,593
Agency CMBS
Schedule of Investments [Line Items]
Amortized Cost	2,691,955		2,378,475
Unrealized Gains	0		11,202
Unrealized Losses	(372,838)		(43,844)
Fair Value	2,319,117		2,345,833
Allowance	0		0
Net Carrying Value	2,691,955		2,378,475
Municipal bonds and notes
Schedule of Investments [Line Items]
Amortized Cost	930,390		705,918
Unrealized Gains	208		51,572
Unrealized Losses	(92,284)		0
Fair Value	838,314		757,490
Allowance	209		214
Net Carrying Value	930,181		705,704
CMBS
Schedule of Investments [Line Items]
Amortized Cost	151,864		169,948
Unrealized Gains	0		3,381
Unrealized Losses	(10,293)		0
Fair Value	141,571		173,329
Allowance	0		0
Net Carrying Value	$ 151,864		$ 169,948