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Managed Investment Entities - Narrative (Details) $ in Millions | 1 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Mar. 31, 2018 USD ($) | Mar. 31, 2017 USD ($) | Jun. 30, 2018 USD ($) collateralizedloanobligation | Jun. 30, 2017 USD ($) 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 |  |  | 16 |  |
Face amount of managed investment entities liabilities purchased by subsidiaries after issuance date |  |  |  | $ 29 |
Amount paid by subsidiaries to purchase managed investment entities liabilities after issuance date |  |  |  | 29 |
Proceeds received by subsidiaries related to sales and redemptions of managed investment entities liabilities |  |  | $ 45 | $ 64 |
Number of collateralized loan obligation entities substantially liquidated, during the period | collateralizedloanobligation |  |  | 1 | 1 |
Difference between aggregate unpaid principal balance and fair value of CLOs' fixed maturity investments |  |  | $ 62 |  | $ 55
Difference between aggregate unpaid principal balance and carrying value of CLOs' debt |  |  | 167 |  | 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 |  |  | 192 | $ 188 | $ 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 |  |  | $ 134 |  |

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