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Securities (Summary of Gross Unrealized Losses and Fair Value of Debt Securities Available-for-Sale with Unrealized Losses) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | $ 880,507 | $ 1,157,774
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | (6,453) | (13,446)
12 Months or More Fair Value | 18,597 | 521,420
12 Months or More Unrealized Losses | (815) | (6,994)
Total Fair Value | 899,104 | 1,679,194
Total Unrealized losses | 7,268 | 20,440
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 575,329 | 1,055,903
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | (3,728) | (12,424)
12 Months or More Fair Value | 18,527 | 491,539
12 Months or More Unrealized Losses | (815) | (6,798)
Total Fair Value | 593,856 | 1,547,442
Total Unrealized losses | 4,543 | 19,222
Asset-backed Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 143,764 | 89,508
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | (2,076) | (880)
12 Months or More Fair Value | 70 | 6,799
12 Months or More Unrealized Losses | 0 | (109)
Total Fair Value | 143,834 | 96,307
Total Unrealized losses | 2,076 | 989
State and Municipal Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 86,471 | 12,363
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | (592) | (142)
12 Months or More Fair Value | 0 | 12,587
12 Months or More Unrealized Losses | 0 | (82)
Total Fair Value | 86,471 | 24,950
Total Unrealized losses | 592 | 224
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 74,943 | 0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | (57) | 0
12 Months or More Fair Value | 0 | 10,495
12 Months or More Unrealized Losses | 0 | (5)
Total Fair Value | 74,943 | 10,495
Total Unrealized losses | $ 57 | $ 5

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