Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 1,122,804	$ 1,136,297
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	21,818	9,413
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	234,461	517,817
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9,539	3,451
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,357,265	1,654,114
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	31,357	12,864
U.S. Government and Federal Agency Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	89,112	31,787
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	949	21
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	25,405
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	21
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	89,112	57,192
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	949	42
Government-Sponsored Enterprise Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	6,155
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	187
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	0
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	0
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	0	6,155
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	0	187
State and Municipal Obligations [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	62,881	6,700
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,844	31
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	1,554
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	1
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	62,881	8,254
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	2,844	32
Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	53,489	652,352
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	1,572	5,306
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	91	147,653
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	867
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	53,580	800,005
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	1,572	6,173
Non-Agency Mortgage-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	288,712	102,931
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,662	254
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	52,529	189,747
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	515	451
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	341,241	292,678
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	3,177	705
Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	530,321	330,876
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	12,879	3,610
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	181,841	152,461
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9,024	2,108
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	712,162	483,337
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	21,903	5,718
Total Mortgage And Asset-Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	872,522	1,086,159
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	17,113	9,170
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	234,461	489,861
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	9,539	3,426
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	1,106,983	1,576,020
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	26,652	12,596
Debt Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	98,289	5,496
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	912	4
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	997
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	3
Debt Securities, Available-for-sale, Unrealized Loss Position, Total	98,289	6,493
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss, Total	$ 912	$ 7

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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