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Securities (Securities Available for Sale) (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | $ 2,299,037 | $ 2,157,610 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 10,231 | 18,352 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (30,691) | (18,268) |
Securities available for sale | 2,278,577 | 2,157,694 |
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract] |  |  |
Available-for-sale Securities, Gross Realized Losses | 0 | 10 | $ 1
Available-for-sale Securities, Gross Realized Gains | 1,181 | 1,591 | $ 553
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 1,486,690 | 1,296,955 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 2,760 | 4,525 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (23,718) | (14,991) |
Securities available for sale | 1,465,732 | 1,286,489 |
State and Municipal Securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 473,914 | 480,417 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 6,343 | 12,690 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (5,197) | (938) |
Securities available for sale | 475,060 | 492,169 |
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 332,348 | 354,515 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 1,065 | 1,113 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (1,511) | (1,846) |
Securities available for sale | 331,902 | 353,782 |
US Treasury Securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 801 | 20,439 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 0 | 0 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (1) | (302) |
Securities available for sale | 800 | 20,137 |
Other Securities [Member] |  |  |
Schedule of Available-for-sale Securities [Line Items] |  |  |
Amortized Cost | 5,284 | 5,284 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 63 | 24 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (264) | (191) |
Securities available for sale | $ 5,083 | $ 5,117 |

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