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Income Taxes - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2017 | Jun. 30, 2016 | Jun. 30, 2017 | Jun. 30, 2016
Income Tax Reconciliation [Line Items] |  |  |  |
Statutory rate of income taxes | 35.00% | 35.00% | 35.00% | 35.00%
Effective tax rate excluding the charge related to the exit of certain lines of business within subsidiaries |  | 36.00% |  | 35.00%
Other lines | Property and Casualty Insurance |  |  |  |
Income Tax Reconciliation [Line Items] |  |  |  |
Special charges related to the exit of certain lines of business within subsidiaries |  | $ 65 |  |
Other lines | Neon Capital Limited | Property and Casualty Insurance |  |  |  |
Income Tax Reconciliation [Line Items] |  |  |  |
Special charges related to the exit of certain lines of business within subsidiaries |  | $ 65 |  |

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