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Accumulated Other Comprehensive Income (Loss) (Components of unrealized holding gains on AFS securities) (Details) - USD ($) $ in Thousands | 3 Months Ended
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Mar. 31, 2019 | Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Unrealized gains (losses) on AFS securities arising during the period | $ 5,954 | $ (8,057)
Tax effect | (1,195) | 1,684
Unrealized gains (losses), net of tax | 4,695 | (6,277)
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 | 5,954 | (8,057)
Tax effect | (1,195) | 1,684
Unrealized gains (losses), net of tax | 4,759 | (6,373)
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 | 265 | (37)
Tax effect | 0 | 0
Unrealized gains (losses), net of tax | 265 | (37)
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 | 5,689 | (8,020)
Tax effect | (1,195) | 1,684
Unrealized gains (losses), net of tax | 4,494 | (6,336)
Accumulated Defined Benefit Plans Adjustment [Member] |  |
Accumulated Other Comprehensive Income (Loss) [Line Items] |  |
Unrealized gains (losses), net of tax | $ 0 | $ 0

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