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Investment Securities Available for Sale (Summary of Available for Sale Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 11,157,760	$ 10,991,506
Gross Unrealized Gains	7,045	66,427
Gross Unrealized Losses	(701,704)	(139,604)
Fair Value	10,463,101	10,918,329
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	414,397	120,465
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(19,811)	(2,627)
Fair Value	394,586	117,838
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	52,865	53,214
Gross Unrealized Gains	411	1,374
Gross Unrealized Losses	(1,471)	(387)
Fair Value	51,805	54,201
Mortgage-backed securities issued by U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	733,289	790,329
Gross Unrealized Gains	60	768
Gross Unrealized Losses	(46,605)	(11,464)
Fair Value	686,744	779,633
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,169,609	8,063,890
Gross Unrealized Gains	4,937	50,491
Gross Unrealized Losses	(553,915)	(102,080)
Fair Value	7,620,631	8,012,301
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	877,362	951,691
Gross Unrealized Gains	326	4,658
Gross Unrealized Losses	(54,810)	(16,726)
Fair Value	822,878	939,623
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	554,868	479,420
Gross Unrealized Gains	1,020	8,644
Gross Unrealized Losses	(25,092)	(6,320)
Fair Value	530,796	481,744
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	337,037	514,188
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	337,037	514,188
Corporate debt securities and other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	18,333	18,309
Gross Unrealized Gains	291	492
Gross Unrealized Losses	0	0
Fair Value	$ 18,624	$ 18,801

X

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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