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Managed Investment Entities - Narrative (Details) $ in Millions | 1 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Mar. 31, 2018 USD ($) | Mar. 31, 2017 USD ($) | Sep. 30, 2018 USD ($) collateralizedloanobligation | Sep. 30, 2017 USD ($) collateralizedloanobligation | Dec. 31, 2017 USD ($)
Variable Interest Entity [Line Items] |  |  |  |  |
Percentage of investment of most subordinate debt tranche, Minimum |  |  | 15.00% |  |
Percentage of investment of most subordinate debt tranche, Maximum |  |  | 60.90% |  |
Number of collateralized loan obligation entities | collateralizedloanobligation |  |  | 15 |  |
Face amount of managed investment entities liabilities purchased by subsidiaries after issuance date |  |  |  | $ 58 |
Amount paid by subsidiaries to purchase managed investment entities liabilities after issuance date |  |  |  | 58 |
Proceeds received by subsidiaries related to sales and redemptions of managed investment entities liabilities |  |  | $ 45 | $ 86 |
Number of collateralized loan obligation entities substantially liquidated, during the period | collateralizedloanobligation |  |  | 1 | 2 |
Difference between aggregate unpaid principal balance and fair value of CLOs' fixed maturity investments |  |  | $ 45 |  | $ 55
Difference between aggregate unpaid principal balance and carrying value of CLOs' debt |  |  | 160 |  | 118
Carrying amount of CLO loans in default |  |  | 1 |  | 1
Aggregate unpaid principal balance of CLO loans in default |  |  | 8 |  | 8
Variable interest entity, primary beneficiary |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Aggregate fair value of investment in collateralized loan obligations |  |  | 191 | $ 261 | $ 215
New Collateralized Loan Obligation Entities |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Face value of liabilities issued by managed investment entities on issuance date | $ 463 | $ 408 |  |  |
Face amount of managed investment entities liabilities purchased by subsidiaries at issuance date | $ 31 | $ 24 |  |  |
Subordinated Debt Obligations | Variable interest entity, primary beneficiary |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |
Aggregate fair value of investment in collateralized loan obligations |  |  | $ 133 |  |

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