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Accumulated Other Comprehensive Income (Loss) (Components of unrealized holding gains on AFS securities) (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Unrealized gains (losses) on AFS securities arising during the period | $ (1,978) | $ 2,570 | $ (10,035) | $ 4,247
Reclassification adjustment for net (gains) losses included in net income | 0 | (142) | 0 | (142)
Tax effect | 442 | (762) | 2,126 | (1,212)
Unrealized gains (losses), net of tax | (1,511) | 1,626 | (7,788) | 2,864
Unrealized Holding Gains (Losses) on AFS Securities [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Unrealized gains (losses) on AFS securities arising during the period | (1,978) | 2,570 | (10,035) | 4,247
Reclassification adjustment for net (gains) losses included in net income | 0 | (142) | 0 | (142)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent | (1,978) | 2,428 | (10,035) | 4,105
Tax effect | 442 | (762) | 2,126 | (1,212)
Unrealized gains (losses), net of tax | (1,536) | 1,666 | (7,909) | 2,893
Unrealized Holding Gains (Losses) on AFS Securities [Member] | Auction Rate Money Market Preferred and Preferred Stocks [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Unrealized gains (losses) on AFS securities arising during the period | 123 | 186 | 86 | 541
Reclassification adjustment for net (gains) losses included in net income | 0 | 0 | 0 | 0
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent | 123 | 186 | 86 | 541
Tax effect | 0 | 0 | 0 | 0
Unrealized gains (losses), net of tax | 123 | 186 | 86 | 541
Unrealized Holding Gains (Losses) on AFS Securities [Member] | All Other AFS Securities [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Unrealized gains (losses) on AFS securities arising during the period | (2,101) | 2,384 | (10,121) | 3,706
Reclassification adjustment for net (gains) losses included in net income | 0 | (142) | 0 | (142)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent | (2,101) | 2,242 | (10,121) | 3,564
Tax effect | 442 | (762) | 2,126 | (1,212)
Unrealized gains (losses), net of tax | (1,659) | 1,480 | (7,995) | 2,352
Accumulated Defined Benefit Plans Adjustment [Member] |  |  |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |  |  |
Unrealized gains (losses), net of tax | $ 0 | $ 0 | $ 0 | $ 0

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