Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 99,075	$ 4,402,724
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,784	250,660
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	9,494,875	7,625,021
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	1,218,700	1,249,972
Debt Securities, Available-for-sale, Unrealized Loss Position	9,593,950	12,027,745
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	1,220,484	1,500,632
US Treasury and Government [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	51,585	605,840
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	809	17,490
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	714,400	380,573
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	24,025	25,940
Debt Securities, Available-for-sale, Unrealized Loss Position	765,985	986,413
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	24,834	43,430
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	25,068
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	4,650
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	43,962	18,040
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	11,696	7,971
Debt Securities, Available-for-sale, Unrealized Loss Position	43,962	43,108
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	11,696	12,621
State and municipal obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	24,022	814,799
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	760	26,708
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,167,607	875,329
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	148,478	171,385
Debt Securities, Available-for-sale, Unrealized Loss Position	1,191,629	1,690,128
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	149,238	198,093
Agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	4,382	1,323,938
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	59	125,330
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	3,875,432	2,966,851
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	720,649	654,327
Debt Securities, Available-for-sale, Unrealized Loss Position	3,879,814	4,290,789
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	720,708	779,657
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	135,984
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	16,736
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	1,152,045	1,069,222
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	173,526	195,218
Debt Securities, Available-for-sale, Unrealized Loss Position	1,152,045	1,205,206
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	173,526	211,954
Asset-backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	19,086	1,331,055
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	156	50,056
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	2,081,293	2,006,188
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	93,076	140,424
Debt Securities, Available-for-sale, Unrealized Loss Position	2,100,379	3,337,243
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	93,232	190,480
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	23,468	2,790,977
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	215	192,122
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	7,108,770	6,042,261
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	987,251	989,969
Debt Securities, Available-for-sale, Unrealized Loss Position	7,132,238	8,833,238
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	987,466	1,182,091
Other debt securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	166,040
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	9,690
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	460,136	308,818
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	47,250	54,707
Debt Securities, Available-for-sale, Unrealized Loss Position	460,136	474,858
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 47,250	$ 64,397