Investment Securities Available for Sale (Schedule of Available for Sale Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 11,174,755	$ 11,273,327
Gross Unrealized Gains	0	2,560
Gross Unrealized Losses	(1,937,564)	(1,597,784)
Fair Value	9,237,191	9,678,103
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	556,791	515,953
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(47,331)	(44,140)
Fair Value	509,460	471,813
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	52,140	52,411
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(4,634)	(3,613)
Fair Value	47,506	48,798
Mortgage-backed securities issued by U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,040,825	904,593
Gross Unrealized Gains	0	1,624
Gross Unrealized Losses	(148,571)	(113,468)
Fair Value	892,254	792,749
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,781,751	8,144,374
Gross Unrealized Gains	0	936
Gross Unrealized Losses	(1,519,999)	(1,250,240)
Fair Value	6,261,752	6,895,070
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	710,600	769,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(131,764)	(114,371)
Fair Value	578,836	655,127
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,023,664	877,590
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(84,929)	(71,645)
Fair Value	938,735	805,945
Corporate debt securities and other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,984	8,908
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(336)	(307)
Fair Value	$ 8,648	$ 8,601