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Principles of Consolidation And Other Matters (Details) - USD ($) | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2020 | Jun. 30, 2019 | Jun. 30, 2020 | Jun. 30, 2019 | Dec. 31, 2019
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |  |
Operating funds related to regulatory requirements or as collateral under captive insurance arrangements | $ 201,000,000 |  | $ 201,000,000 |  | $ 197,000,000
Equity method investments lag period |  |  | 3 months |  |
Gain (loss) on investment income, net | (31,000,000) | $ 8,000,000 | $ (33,000,000) | $ 13,000,000 |
Gain (loss) on equity securities | $ (2,000,000) | $ 3,000,000 | $ (3,000,000) | $ 6,000,000 |
Effective tax rate (as a percent) | 26.20% | 37.40% | 24.90% | 28.20% |
Unrecognized tax benefits | $ 79,000,000 |  | $ 79,000,000 |  | $ 86,000,000
Minimum |  |  |  |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |  |
Reasonably possible decrease in unrecognized tax benefits | 0 |  | 0 |  |
Maximum |  |  |  |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |  |
Reasonably possible decrease in unrecognized tax benefits | 12,000,000 |  | 12,000,000 |  |
Private Equity Funds |  |  |  |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |  |
Equity method income | (6,000,000) | $ 5,000,000 | (7,000,000) | $ 7,000,000 |
Alexander Forbes Group Holdings Limited |  |  |  |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |  |
Gain (loss) on investment income, net | $ (23,000,000) |  | $ (23,000,000) |  |

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