Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($)	Dec. 31, 2023	Dec. 31, 2022
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	$ 10,904,765,000	$ 13,738,206,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	479,000	742,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(1,220,484,000)	(1,500,632,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	9,684,760,000	12,238,316,000
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	841,267,000	1,078,807,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	81,000	29,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(24,834,000)	(43,430,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	816,514,000	1,035,406,000
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	55,658,000	55,729,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	0	0
Available For Sale Securities, Gross Unrealized Loss at Period End	(11,696,000)	(12,621,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	43,962,000	43,108,000
State and municipal obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,346,633,000	1,965,028,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	24,000	174,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(149,238,000)	(198,093,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	1,197,419,000	1,767,109,000
Agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	4,621,821,000	5,087,893,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	233,000	191,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(720,708,000)	(779,657,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	3,901,346,000	4,308,427,000
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	1,331,288,000	1,423,469,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	136,000	92,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(173,526,000)	(211,954,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	1,157,898,000	1,211,607,000
Asset-backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	2,200,712,000	3,588,025,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	5,000	256,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(93,232,000)	(190,480,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	2,107,485,000	3,397,801,000
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	8,153,821,000	10,099,387,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	374,000	539,000
Available For Sale Securities, Gross Unrealized Loss at Period End	(987,466,000)	(1,182,091,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	7,166,729,000	8,917,835,000
Other Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Amortized Cost	507,386,000	539,255,000
Available For Sale Securities, Gross Unreailzed Gain at Period End	0	0
Available For Sale Securities, Gross Unrealized Loss at Period End	(47,250,000)	(64,397,000)
Debt Securities, Available-for-sale, Allowance for Credit Loss	0	0
Debt Securities, Available-for-sale, Fair Value	$ 460,136,000	$ 474,858,000