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Basis of Presentation - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2018 | Jun. 30, 2017 | Jun. 30, 2018 | Jun. 30, 2017
Basis of Presentation [Line Items] |  |  |  |
Cumulative effect of change in accounting principle (3) | $ 0 | $ 0 | $ (15,041) | $ 0
Future lease commitments | 8,416 |  | 8,416 |
Retained earnings |  |  |  |
Basis of Presentation [Line Items] |  |  |  |
Cumulative effect of change in accounting principle (3) |  |  | 15,041 | 0
Accumulated other comprehensive income, net of tax: |  |  |  |
Basis of Presentation [Line Items] |  |  |  |
Cumulative effect of change in accounting principle (3) |  |  | (15,041) | $ 0
Stranded Tax Amounts Reclassified |  |  | 47,900 |
Net Unrealized Investment Gains and Losses on Fixed Maturity and Equity Securities |  |  |  |
Basis of Presentation [Line Items] |  |  |  |
Cumulative effect of change in accounting principle (3) | 0 |  | (15,041) |
Stranded Tax Amounts Reclassified |  |  | 50,034 |
Benefit Plans |  |  |  |
Basis of Presentation [Line Items] |  |  |  |
Cumulative effect of change in accounting principle (3) | $ 0 |  | 0 |
Stranded Tax Amounts Reclassified |  |  | $ (2,134) |

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- Definition Tax Cuts And Jobs Act Of 2017, Reclassification From AOCI To Retained Earnings, Tax Effect + References No definition available. + Details
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