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Investments Investments (Entities That Calculate Net Asset Value Per Share) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 4,921 | $ 4,244
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | 3,263 | 3,705
Financial [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | 611 | 596
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 329 | $ 193
Financial [Member] | Minimum [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 2 years | 2 years
Financial [Member] | Maximum |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 10 years | 10 years
Real Estate Funds [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 712 | $ 704
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 422 | $ 362
Real Estate Funds [Member] | Minimum [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 2 years | 2 years
Real Estate Funds [Member] | Maximum |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 11 years | 11 years
Distressed Alternative Investments [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 263 | $ 296
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 80 | $ 105
Distressed Alternative Investments [Member] | Minimum [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 2 years | 2 years
Distressed Alternative Investments [Member] | Maximum |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 7 years | 7 years
Private Credit Alternative Investments [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 104 | $ 147
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 272 | $ 310
Private Credit Alternative Investments [Member] | Minimum [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 3 years | 3 years
Private Credit Alternative Investments [Member] | Maximum |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 8 years | 8 years
Private Equity Funds [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 2,844 | $ 2,362
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 2,160 | $ 2,735
Private Equity Funds [Member] | Minimum [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 2 years | 2 years
Private Equity Funds [Member] | Maximum |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 14 years | 14 years
Vintage Alternative Investments [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 116 | $ 56
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 0 | $ 0
Vintage Alternative Investments [Member] | Minimum [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 1 year | 1 year
Vintage Alternative Investments [Member] | Maximum |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Liquidating Investment, Remaining Period | 2 years | 2 years
Investment Funds Alternative Investments [Member] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items] |  |
Alternative Investment | $ 271 | $ 83
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | $ 0 | $ 0

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- Definition Fair value of investment other than investment in equity security, investment in debt security and equity method investment. Includes, but is not limited to, investment in certain entities that calculate net asset value per share. Example includes, but is not limited to, investment in hedge fund, venture capital fund, private equity fund, and real estate partnership or fund. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 35 -Paragraph 54B -URI http://asc.fasb.org/extlink&oid=117332851&loc=SL7495116-110257 + Details
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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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- Definition Remaining period of expected liquidation by investee of underlying asset of investment measured at net asset value per share or unit. In 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258 + Details
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- Definition The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=117815213&loc=SL6742756-110258 + Details
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