Investment Securities (Securities With Unrealized Losses And Length Of Impairment Period) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	$ 694,458	$ 1,136,297
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,741	9,413
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	253,734	517,817
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,617	3,451
Debt Securities, Available-for-sale, Unrealized Loss Position	948,192	1,654,114
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	6,358	12,864
US Treasury and Government [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	0	31,787
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	0	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	0	57,192
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	0	42
US Government-sponsored Enterprise Debt Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	19,720	6,155
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	98	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	19,720	6,155
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	98	187
State and municipal obligations [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	45,622	6,700
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	230	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	45,622	8,254
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	230	32
Agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	470,373	652,352
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	2,802	5,306
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	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	470,373	800,005
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	2,802	6,173
Non-agency mortgage-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	112,861	102,931
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	380	254
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	0	189,747
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	0	451
Debt Securities, Available-for-sale, Unrealized Loss Position	112,861	292,678
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	380	705
Asset-backed Securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	21,360	330,876
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	56	3,610
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	253,734	152,461
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,617	2,108
Debt Securities, Available-for-sale, Unrealized Loss Position	275,094	483,337
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	2,673	5,718
Total mortgage and asset-backed securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	604,594	1,086,159
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	3,238	9,170
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer	253,734	489,861
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	2,617	3,426
Debt Securities, Available-for-sale, Unrealized Loss Position	858,328	1,576,020
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	5,855	12,596
Other debt securities [Member]
Investment [Line Items]
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months	24,522	5,496
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	175	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	24,522	6,493
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss	$ 175	$ 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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