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Income Taxes - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2017 | Sep. 30, 2016 | Jun. 30, 2016 | Sep. 30, 2017 | Sep. 30, 2016
Income Tax Reconciliation [Line Items] |  |  |  |  |
Statutory rate of income taxes | 35.00% | 35.00% |  | 35.00% | 35.00%
Current year catastrophe losses |  |  |  | $ 2,237 | $ 2,011
Effective tax rate excluding the catastrophe losses within subsidiaries | 22.00% |  |  |  |
Effective tax rate excluding the charge related to the exit of certain lines of business within subsidiaries |  | 36.00% |  |  | 36.00%
Operating loss carryforwards | $ 13 |  |  | $ 13 |
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 |  |  |
Hurricanes and Earthquakes | Neon Capital Limited |  |  |  |  |
Income Tax Reconciliation [Line Items] |  |  |  |  |
Current year catastrophe losses | $ 53 |  |  |  |

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- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
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