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Shareholders' Equity - AOCI Components (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Sep. 30, 2017
Repurchase of shares |  |  |
Repurchase of common stock (in shares) | 0 | 0 |
After-tax amounts: |  |  |
Accumulated other comprehensive income (loss), after tax | $ (5,221) |  | $ 2,300
Maximum |  |  |
Repurchase of shares |  |  |
Number of common shares authorized to be repurchased | 4,000,000 |  |
Unrealized appreciation (depreciation) on securities |  |  |
Pre-tax amounts: |  |  |
Accumulated other comprehensive income (loss) before tax | $ 19,908 |  | 31,700
After-tax amounts: |  |  |
Accumulated other comprehensive income (loss), after tax | 11,901 |  | 20,070
Defined benefit pension plan |  |  |
Pre-tax amounts: |  |  |
Accumulated other comprehensive income (loss) before tax | (27,952) |  | (28,873)
After-tax amounts: |  |  |
Accumulated other comprehensive income (loss), after tax | (17,122) |  | (17,770)
Accumulated Other Comprehensive Loss |  |  |
Pre-tax amounts: |  |  |
Accumulated other comprehensive income (loss) before tax | (8,044) |  | 2,827
After-tax amounts: |  |  |
Accumulated other comprehensive income (loss), after tax | $ (5,221) |  | $ 2,300

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