Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)	Mar. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 10,097,801,000	$ 10,127,426,000
Gross Unrealized Gains	22,425,000	3,961,000
Gross Unrealized Losses	(855,279,000)	(994,534,000)
Allowance for Credit Losses	0	0
Fair Value	9,264,947,000	9,136,853,000
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,626,515,000	2,594,130,000
Gross Unrealized Gains	16,685,000	2,981,000
Gross Unrealized Losses	(16,565,000)	(41,859,000)
Allowance for Credit Losses	0	0
Fair Value	2,626,635,000	2,555,252,000
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,041,000	55,425,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(10,985,000)	(12,576,000)
Allowance for Credit Losses	0	0
Fair Value	44,056,000	42,849,000
State and municipal obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	789,579,000	822,790,000
Gross Unrealized Gains	0	16,000
Gross Unrealized Losses	(68,392,000)	(79,915,000)
Allowance for Credit Losses	0	0
Fair Value	721,187,000	742,891,000
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,098,966,000	4,195,182,000
Gross Unrealized Gains	611,000	415,000
Gross Unrealized Losses	(669,011,000)	(750,706,000)
Allowance for Credit Losses	0	0
Fair Value	3,430,566,000	3,444,891,000
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	614,798,000	625,539,000
Gross Unrealized Gains	296,000	136,000
Gross Unrealized Losses	(48,968,000)	(56,986,000)
Allowance for Credit Losses	0	0
Fair Value	566,126,000	568,689,000
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,652,018,000	1,595,797,000
Gross Unrealized Gains	4,156,000	413,000
Gross Unrealized Losses	(30,892,000)	(39,195,000)
Allowance for Credit Losses	0	0
Fair Value	1,625,282,000	1,557,015,000
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,365,782,000	6,416,518,000
Gross Unrealized Gains	5,063,000	964,000
Gross Unrealized Losses	(748,871,000)	(846,887,000)
Allowance for Credit Losses	0	0
Fair Value	5,621,974,000	5,570,595,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	260,884,000	238,563,000
Gross Unrealized Gains	677,000	0
Gross Unrealized Losses	(10,466,000)	(13,297,000)
Allowance for Credit Losses	0	0
Fair Value	$ 251,095,000	$ 225,266,000