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Fair Value (Table of reconciliation for assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | $ 407 | $ 473
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 9 | 5
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 9 | (4)
Purchases | 126 | 296
Sales | (68) | (61)
Settlements | (102) | (157)
Transfers into Level 3 | 169 | 61
Transfers out of Level 3 | (96) | (206)
Balance, Ending, Assets | 454 | 407
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | 0 | (5)
Corporate and other bonds |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | 130 | 168
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 0 | 1
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 3 | 1
Purchases | 18 | 163
Sales | (5) | (36)
Settlements | (54) | (103)
Transfers into Level 3 | 16 | 0
Transfers out of Level 3 | (10) | (64)
Balance, Ending, Assets | 98 | 130
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | 0 | 0
States, municipalities and political subdivisions |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | 1 | 2
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 0 | 0
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 0 | 0
Purchases | 0 | 0
Sales | 0 | 0
Settlements | 0 | (1)
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 0 | 0
Balance, Ending, Assets | 1 | 1
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | 0 | 0
Asset-backed |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | 199 | 209
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 2 | 0
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 3 | (5)
Purchases | 107 | 133
Sales | 0 | (25)
Settlements | (43) | (32)
Transfers into Level 3 | 153 | 61
Transfers out of Level 3 | (86) | (142)
Balance, Ending, Assets | 335 | 199
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | 0 | 0
Equity securities |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | 19 | 20
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 0 | (1)
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 3 | 0
Purchases | 1 | 0
Sales | (3) | 0
Settlements | 0 | 0
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 0 | 0
Balance, Ending, Assets | 20 | 19
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | 0 | (2)
Derivative financial instruments |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | 0 |
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 1 |
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 0 |
Purchases | 0 |
Sales | (1) |
Settlements | 0 |
Transfers into Level 3 | 0 |
Transfers out of Level 3 | 0 |
Balance, Ending, Assets | 0 | 0
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | 0 |
Life settlement contracts, included in Other assets |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] |  |
Balance, Beginning, Assets | 58 | 74
Net realized investment gains (losses) and net change in unrealized appreciation (depreciation) included in Net income (loss) | 6 | 5
Net change in unrealized appreciation (depreciation) included in Other comprehensive income (loss) | 0 | 0
Purchases | 0 | 0
Sales | (59) | 0
Settlements | (5) | (21)
Transfers into Level 3 | 0 | 0
Transfers out of Level 3 | 0 | 0
Balance, Ending, Assets | 0 | 58
Unrealized gains (losses) on Level 3 assets and liabilities recognized in Net income (loss) | $ 0 | $ (3)

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- Definition Amount of unrealized (holding) gain (loss) which is included in the statement of income (or changes in net assets) related to those assets still held at the reporting date for which fair value is measured on a recurring basis using significant unobservable inputs (Level 3). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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- Definition Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
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