Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 11,833,736,000	$ 13,738,206,000
Gross Unrealized Gains	282,000	742,000
Gross Unrealized Losses	(1,419,393,000)	(1,500,632,000)
Allowance for Credit Losses	0	0
Fair Value	10,414,625,000	12,238,316,000
U.S. government and federal agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	984,984,000	1,078,807,000
Gross Unrealized Gains	0	29,000
Gross Unrealized Losses	(39,169,000)	(43,430,000)
Allowance for Credit Losses	0	0
Fair Value	945,815,000	1,035,406,000
Government-sponsored enterprise obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,681,000	55,729,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(11,645,000)	(12,621,000)
Allowance for Credit Losses	0	0
Fair Value	44,036,000	43,108,000
State and municipal obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,401,610,000	1,965,028,000
Gross Unrealized Gains	0	174,000
Gross Unrealized Losses	(173,873,000)	(198,093,000)
Allowance for Credit Losses	0	0
Fair Value	1,227,737,000	1,767,109,000
Agency mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,849,215,000	5,087,893,000
Gross Unrealized Gains	84,000	191,000
Gross Unrealized Losses	(783,893,000)	(779,657,000)
Allowance for Credit Losses	0	0
Fair Value	4,065,406,000	4,308,427,000
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,378,516,000	1,423,469,000
Gross Unrealized Gains	72,000	92,000
Gross Unrealized Losses	(203,798,000)	(211,954,000)
Allowance for Credit Losses	0	0
Fair Value	1,174,790,000	1,211,607,000
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,646,850,000	3,588,025,000
Gross Unrealized Gains	126,000	256,000
Gross Unrealized Losses	(147,301,000)	(190,480,000)
Allowance for Credit Losses	0	0
Fair Value	2,499,675,000	3,397,801,000
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,874,581,000	10,099,387,000
Gross Unrealized Gains	282,000	539,000
Gross Unrealized Losses	(1,134,992,000)	(1,182,091,000)
Allowance for Credit Losses	0	0
Fair Value	7,739,871,000	8,917,835,000
Other debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	516,880,000	539,255,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(59,714,000)	(64,397,000)
Allowance for Credit Losses	0	0
Fair Value	$ 457,166,000	$ 474,858,000