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Basis of Presentation - Narrative (Details) - USD ($) $ in Thousands | 3 Months Ended |
--- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Dec. 31, 2017
Basis of Presentation [Line Items] |  |  |
Cumulative effect of change in accounting principle (3) | $ (15,041) | $ 0 |
Future lease commitments |  |  | $ 9,093
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) | (15,041) |  |
Stranded Tax Amounts Reclassified | 50,034 |  |
Benefit Plans |  |  |
Basis of Presentation [Line Items] |  |  |
Cumulative effect of change in accounting principle (3) | 0 |  |
Stranded Tax Amounts Reclassified | $ (2,134) |  |

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- Definition Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 3) -URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717 + Details
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