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v3.20.4

Investments (Allowance rollforward) (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2020 USD ($)
Fair Value [Line Items] |  |
Allowance for Credit Loss, Ending Balance | $ (27) |
Corporate debt securities [Member] |  |
Fair Value [Line Items] |  |
Allowance for Credit Loss, Beginning Balance | 0 | [1]
Allowance for Credit Loss, Not Previously Recorded | 13 |
Allowance for Credit Loss, Period Increase (Decrease) | (3) |
Allowance for Credit Loss, Ending Balance | 10 |
Asset-backed Securities [Member] |  |
Fair Value [Line Items] |  |
Allowance for Credit Loss, Beginning Balance | 0 | [1]
Allowance for Credit Loss, Not Previously Recorded | 1 |
Allowance for Credit Loss, Period Increase (Decrease) | 0 |
Allowance for Credit Loss, Ending Balance | 1 |
Total available-for-sale securities [Member] |  |
Fair Value [Line Items] |  |
Allowance for Credit Loss, Beginning Balance | 0 | [1]
Allowance for Credit Loss, Not Previously Recorded | 14 |
Allowance for Credit Loss, Period Increase (Decrease) | (3) |
Allowance for Credit Loss, Ending Balance | $ 11 |
[1] | Prior to January 1, 2020, credit losses on Available-for-Sale securities were not recorded in an allowance but were recorded as a reduction of the book value of the security if the security was other-than-temporarily impaired. There is no adoption impact due to the prospective transition for Available-for-Sale securities.

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