Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 9,333,626,000	$ 9,742,278,000
Gross Unrealized Gains	23,944,000	45,329,000
Gross Unrealized Losses	(711,443,000)	(692,094,000)
Allowance for Credit Losses	0	0
Fair Value	8,646,127,000	9,095,513,000
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,147,185,000	3,257,561,000
Gross Unrealized Gains	16,508,000	32,403,000
Gross Unrealized Losses	(16,400,000)	(10,864,000)
Allowance for Credit Losses	0	0
Fair Value	3,147,293,000	3,279,100,000
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	54,599,000	54,951,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(10,614,000)	(10,239,000)
Allowance for Credit Losses	0	0
Fair Value	43,985,000	44,712,000
State and municipal obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	705,864,000	715,037,000
Gross Unrealized Gains	13,000	37,000
Gross Unrealized Losses	(51,053,000)	(50,341,000)
Allowance for Credit Losses	0	0
Fair Value	654,824,000	664,733,000
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,701,146,000	3,786,811,000
Gross Unrealized Gains	1,363,000	1,380,000
Gross Unrealized Losses	(578,840,000)	(565,086,000)
Allowance for Credit Losses	0	0
Fair Value	3,123,669,000	3,223,105,000
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	446,168,000	467,200,000
Gross Unrealized Gains	274,000	430,000
Gross Unrealized Losses	(31,665,000)	(31,942,000)
Allowance for Credit Losses	0	0
Fair Value	414,777,000	435,688,000
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,104,943,000	1,269,503,000
Gross Unrealized Gains	5,159,000	9,503,000
Gross Unrealized Losses	(16,283,000)	(16,961,000)
Allowance for Credit Losses	0	0
Fair Value	1,093,819,000	1,262,045,000
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,252,257,000	5,523,514,000
Gross Unrealized Gains	6,796,000	11,313,000
Gross Unrealized Losses	(626,788,000)	(613,989,000)
Allowance for Credit Losses	0	0
Fair Value	4,632,265,000	4,920,838,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	173,721,000	191,215,000
Gross Unrealized Gains	627,000	1,576,000
Gross Unrealized Losses	(6,588,000)	(6,661,000)
Allowance for Credit Losses	0	0
Fair Value	$ 167,760,000	$ 186,130,000