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Other Comprehensive Income/Loss - Schedule of Comprehensive Income (Loss) (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Investment securities available-for sale: |  |  |  |
Change in net unrealized gain during period, pre-tax | $ 4.2 | $ (6.3) | $ 58.0 | $ (33.9)
Change in net unrealized gain during period, tax expense (benefit) | 1.0 | (1.7) | 15.0 | (8.9)
Change in net unrealized gain during period, net of tax | 3.2 | (4.6) | 43.0 | (25.0)
Reclassification adjustment for net (gains) losses included in income | (0.1) | 0.0 | (0.1) | 0.0
Reclassification adjustment for net (gains) losses included in income, Tax Expense (Benefit) | 0.0 | 0.0 | 0.0 | 0.0
Reclassification adjustment for net (gains) losses included in income, Net of Tax | (0.1) | 0.0 | (0.1) | 0.0
Reclassification adjustment for securities transferred from held-to-maturity to available-for-sale, pre-tax | 0.0 | 0.0 | (6.0) | 0.0
Reclassification adjustment for securities transferred from held-to-maturity to available-for-sale, tax expense (benefit) |  |  | (1.6) | 0.0
Reclassification adjustment for securities transferred from held-to-maturity to available-for-sale, net of tax |  |  | (4.4) | 0.0
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity, pre-tax | 0.0 | 0.5 | 0.0 | 1.5
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity, tax expense (benefit) | 0.0 | 0.1 | 0.0 | 0.4
Change in unamortized loss on available-for-sale securities transferred into held-to-maturity, net of tax | 0.0 | 0.4 | 0.0 | 1.1
Defined benefits post-retirement benefit plan: |  |  |  |
Change in net actuarial (gain) loss, pre-tax | (0.2) | (0.2) | (0.5) | (0.5)
Change in net actuarial (gain) loss, tax expense (benefit) | 0.0 |  | 0.0 | (0.1)
Change in net actuarial (gain) loss, net of tax | (0.2) | (0.2) | (0.5) | (0.4)
Other comprehensive income (loss), before tax | 3.9 | (6.0) | 51.4 | (32.9)
Total other comprehensive income, tax expense (benefit) | 1.0 | (1.6) | 13.4 | (8.6)
Total other comprehensive income, net of tax amount | $ 2.9 | $ (4.4) | $ 38.0 | $ (24.3)

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