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Investment Securities Available for Sale (Schedule of Available for Sale Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 11,173,873	$ 11,273,327
Gross Unrealized Gains	508	2,560
Gross Unrealized Losses	(1,553,206)	(1,597,784)
Fair Value	9,621,175	9,678,103
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	517,626	515,953
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(43,736)	(44,140)
Fair Value	473,890	471,813
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	52,397	52,411
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3,794)	(3,613)
Fair Value	48,603	48,798
Mortgage-backed securities issued by U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	928,031	904,593
Gross Unrealized Gains	0	1,624
Gross Unrealized Losses	(110,681)	(113,468)
Fair Value	817,350	792,749
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,979,131	8,144,374
Gross Unrealized Gains	508	936
Gross Unrealized Losses	(1,202,246)	(1,250,240)
Fair Value	6,777,393	6,895,070
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	732,938	769,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(116,987)	(114,371)
Fair Value	615,951	655,127
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	954,792	877,590
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(75,442)	(71,645)
Fair Value	879,350	805,945
Corporate debt securities and other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,958	8,908
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(320)	(307)
Fair Value	$ 8,638	$ 8,601

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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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