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Statutory Financial Information and Dividend Limitations - Allstates domestic insurance subsidiaries (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Amount per statutory accounting practices |  |  |
Net income (loss) | $ 3,377 | $ 1,717 | $ 1,770
Capital and surplus | 18,630 | 16,819 |
Property-Liability |  |  |
Amount per statutory accounting practices |  |  |
Net income (loss) | 3,050 | 1,520 | 1,826
Capital and surplus | 14,903 | 13,436 |
Allstate Financial |  |  |
Amount per statutory accounting practices |  |  |
Net income (loss) | 327 | 197 | $ (56)
Capital and surplus | $ 3,727 | $ 3,383 |

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- Definition The amount of statutory capital and surplus (stockholders' equity) as of the balance sheet date using prescribed or permitted statutory accounting practices (rather than GAAP, if different) of the state or country. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 505 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6486098&loc=d3e24708-158529 + Details
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- Definition Amount of net income for the period determined using accounting principles prescribed or permitted by insurance regulators. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(23)(c)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 + Details
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