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Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) security | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Equity Securities, FV-NI, Gain (Loss) | [1] | $ 0 | $ (195) |  | $ 0
Less than 12 Months Fair Value |  | 1,157,774 | 276,306 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant |  | (13,446) | (1,598) |  |
12 Months or More Fair Value |  | 521,420 | 1,873,565 |  |
12 Months or More Unrealized Losses |  | (6,994) | (54,368) |  |
Total Fair Value |  | 1,679,194 | 2,149,871 |  |
Total Unrealized Losses |  | $ (20,440) | (55,966) |  |
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security |  | 243 |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security |  | 162 |  |  |
Less than 12 Months Fair Value | [2] | $ 1,055,903 | 114,551 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | [2] | (12,424) | (750) |  |
12 Months or More Fair Value | [2] | 491,539 | 1,207,020 |  |
12 Months or More Unrealized Losses | [2] | (6,798) | (40,096) |  |
Total Fair Value | [2] | 1,547,442 | 1,321,571 |  |
Total Unrealized Losses | [2] | $ (19,222) | (40,846) |  |
Asset-backed Securities [Member] |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security |  | 18 |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security |  | 6 |  |  |
Less than 12 Months Fair Value | [2] | $ 89,508 | 40,071 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant | [2] | (880) | (222) |  |
12 Months or More Fair Value | [2] | 6,799 | 94,367 |  |
12 Months or More Unrealized Losses | [2] | (109) | (2,399) |  |
Total Fair Value | [2] | 96,307 | 134,438 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Accumulated Loss | [2] | $ (989) | (2,621) |  |
State and Municipal Securities [Member] |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security |  | 24 |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security |  | 14 |  |  |
Less than 12 Months Fair Value |  | $ 12,363 | 106,292 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant |  | (142) | (581) | [2] |
12 Months or More Fair Value |  | 12,587 | 280,496 |  |
12 Months or More Unrealized Losses |  | (82) | (7,179) |  |
Total Fair Value |  | 24,950 | 386,788 |  |
Total Unrealized Losses |  | $ (224) | (7,760) |  |
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member] |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security |  | 3 |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security |  | 3 |  |  |
Less than 12 Months Fair Value |  | $ 0 | 15,392 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant |  | 0 | (45) |  |
12 Months or More Fair Value |  | 10,495 | 291,435 |  |
12 Months or More Unrealized Losses |  | (5) | (4,691) |  |
Total Fair Value |  | 10,495 | 306,827 |  |
Total Unrealized Losses |  | $ (5) | (4,736) |  |
US Government Securities [Member] |  |  |  |  |
Debt Securities, Available-for-sale [Line Items] |  |  |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions | security |  | 0 |  |  |
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year | security |  | 0 |  |  |
Less than 12 Months Fair Value |  |  | 0 |  |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant |  |  | 0 |  |
12 Months or More Fair Value |  |  | 247 |  |
12 Months or More Unrealized Losses |  |  | (3) |  |
Total Fair Value |  |  | 247 |  |
Total Unrealized Losses |  |  | $ (3) |  |
[1] | Other securities losses, net includes net unrealized loss activity associated with equity securities.
[2] | Beginning in 2019, other asset-backed securities were presented separately in this table. Prior period amounts that were previously reported in U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations have been reclassified to conform to current period presentation.

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