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Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | $ 580,986 | $ 1,157,774
Less than 12 Months Unrealized Losses | (4,212) | (13,446)
12 Months or More Fair Value | 23,179 | 521,420
12 Months or More Unrealized Losses | (840) | (6,994)
Total Fair Value | 604,165 | 1,679,194
Total Unrealized Losses | (5,052) | (20,440)
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 318,868 | 1,055,903
Less than 12 Months Unrealized Losses | (2,817) | (12,424)
12 Months or More Fair Value | 23,084 | 491,539
12 Months or More Unrealized Losses | (840) | (6,798)
Total Fair Value | 341,952 | 1,547,442
Total Unrealized Losses | (3,657) | (19,222)
Asset-backed Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 71,552 | 89,508
Less than 12 Months Unrealized Losses | (530) | (880)
12 Months or More Fair Value | 95 | 6,799
12 Months or More Unrealized Losses | 0 | (109)
Total Fair Value | 71,647 | 96,307
Total Unrealized Losses | (530) | (989)
State and Municipal Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 90,620 | 12,363
Less than 12 Months Unrealized Losses | (813) | (142)
12 Months or More Fair Value | 0 | 12,587
12 Months or More Unrealized Losses | 0 | (82)
Total Fair Value | 90,620 | 24,950
Total Unrealized Losses | (813) | (224)
U.S. Government and Government-Sponsored Enterprise Securities [Member] |  |
Debt Securities, Available-for-sale [Line Items] |  |
Less than 12 Months Fair Value | 99,946 | 0
Less than 12 Months Unrealized Losses | (52) | 0
12 Months or More Fair Value | 0 | 10,495
12 Months or More Unrealized Losses | 0 | (5)
Total Fair Value | 99,946 | 10,495
Total Unrealized Losses | $ (52) | $ (5)

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