Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 12,538,550,000	$ 13,738,206,000
Gross Unrealized Gains	1,981,000	742,000
Gross Unrealized Losses	(1,311,915,000)	(1,500,632,000)
Allowance for Credit Losses	0	0
Fair Value	11,228,616,000	12,238,316,000
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,048,755,000	1,078,807,000
Gross Unrealized Gains	1,477,000	29,000
Gross Unrealized Losses	(30,009,000)	(43,430,000)
Allowance for Credit Losses	0	0
Fair Value	1,020,223,000	1,035,406,000
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,689,000	55,729,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(11,275,000)	(12,621,000)
Allowance for Credit Losses	0	0
Fair Value	44,414,000	43,108,000
State and municipal obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,615,170,000	1,965,028,000
Gross Unrealized Gains	218,000	174,000
Gross Unrealized Losses	(161,574,000)	(198,093,000)
Allowance for Credit Losses	0	0
Fair Value	1,453,814,000	1,767,109,000
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,975,242,000	5,087,893,000
Gross Unrealized Gains	183,000	191,000
Gross Unrealized Losses	(703,862,000)	(779,657,000)
Allowance for Credit Losses	0	0
Fair Value	4,271,563,000	4,308,427,000
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,403,543,000	1,423,469,000
Gross Unrealized Gains	103,000	92,000
Gross Unrealized Losses	(195,677,000)	(211,954,000)
Allowance for Credit Losses	0	0
Fair Value	1,207,969,000	1,211,607,000
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,918,160,000	3,588,025,000
Gross Unrealized Gains	0	256,000
Gross Unrealized Losses	(154,582,000)	(190,480,000)
Allowance for Credit Losses	0	0
Fair Value	2,763,578,000	3,397,801,000
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,296,945,000	10,099,387,000
Gross Unrealized Gains	286,000	539,000
Gross Unrealized Losses	(1,054,121,000)	(1,182,091,000)
Allowance for Credit Losses	0	0
Fair Value	8,243,110,000	8,917,835,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	521,991,000	539,255,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(54,936,000)	(64,397,000)
Allowance for Credit Losses	0	0
Fair Value	$ 467,055,000	$ 474,858,000