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Investments Investments - Equity Investments (Details) - USD ($) $ in Millions | Mar. 31, 2020 | Dec. 31, 2019
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Schedule of Equity Method Investments [Line Items] |  |
Other investments | $ 363 | $ 478
Real Estate [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 15 | 16
Hedge Funds, Multi-strategy [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 60 | 65
Interest Rate Contract [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 57 | 176
Illiquid Investments [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 47 | 51
Insurance Linked [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 3 | 3
Equity [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 58 | 55
Credit Index Product [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 52 | 66
Private Equity Funds [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 4 | 0
Emerging Market Debt [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 16 | 0
Equity investments in pooled funds [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 312 | 432
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 17 | 81
Priced Through Pricing Vendors [Member] | Equity [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 48 | 55
Priced Through Pricing Vendors [Member] | Emerging Market Debt [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 16 | $ 0
Commitments [Member] | Partnership Interest [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | $ 76 |

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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