Investment Securities Available for Sale (Summary of Available for Sale Investment Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 11,175,791	$ 11,273,327
Gross Unrealized Gains	2,994	2,560
Gross Unrealized Losses	(1,446,167)	(1,597,784)
Fair Value	9,732,618	9,678,103
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	516,782	515,953
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(36,502)	(44,140)
Fair Value	480,280	471,813
U.S. Government agency securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	52,397	52,411
Gross Unrealized Gains	1	0
Gross Unrealized Losses	(3,453)	(3,613)
Fair Value	48,945	48,798
Mortgage-backed securities issued by U.S. Government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	810,042	904,593
Gross Unrealized Gains	202	1,624
Gross Unrealized Losses	(101,699)	(113,468)
Fair Value	708,545	792,749
Mortgage-backed securities issued by U.S. Government sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,159,830	8,144,374
Gross Unrealized Gains	2,791	936
Gross Unrealized Losses	(1,137,121)	(1,250,240)
Fair Value	7,025,500	6,895,070
Collateralized mortgage obligations issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	753,877	769,498
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(105,318)	(114,371)
Fair Value	648,559	655,127
Commercial mortgage-backed securities issued by U.S. Government agencies or sponsored enterprises
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	873,930	877,590
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(61,907)	(71,645)
Fair Value	812,023	805,945
Corporate debt securities and other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,933	8,908
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(167)	(307)
Fair Value	$ 8,766	$ 8,601