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Investments Investments - Equity Investments (Details) - USD ($) $ in Millions | Mar. 31, 2021 | Dec. 31, 2020
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Real Estate [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | $ 16 | $ 16
Hedge Funds, Multi-strategy [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 210 | 196
Interest Rate Contract [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 77 | 78
Illiquid Investments [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 67 | 65
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 | 82 | 73
Credit Index Product [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 98 | 73
Private Equity Funds [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 14 | 13
Emerging Market Debt [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 33 | 25
Equity investments in pooled funds [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 600 | 543
Priced Through Pricing Vendors [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 99 | 89
Priced Through Pricing Vendors [Member] | Interest Rate Contract [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 0 | 3
Priced Through Pricing Vendors [Member] | Equity [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 66 | 60
Priced Through Pricing Vendors [Member] | Emerging Market Debt [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | 33 | $ 25
Commitments [Member] | Partnership Interest [Member] |  |
Schedule of Equity Method Investments [Line Items] |  |
Other investments | $ 102 |

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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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