Fair Value Measurements - Assets at Fair Value Recurring Basis (Details) - USD ($) $ in Millions | Jun. 30, 2022 | Dec. 31, 2021 |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | $ 1,700 | $ 1,907 |
Other securities | 73 | 85 |
U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 13 | 16 |
Obligations of states, municipalities, and political subdivisions | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 69 | 79 |
Corporate debt | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 1,122 | 1,302 |
RMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 175 | 170 |
CMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 39 | 45 |
CDO/ABS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 87 | 90 |
Level 1 | | |
Investments, Debt and Equity Securities [Abstract] | | |
Total investment securities | 51 | 59 |
Level 2 | | |
Investments, Debt and Equity Securities [Abstract] | | |
Total investment securities | 1,718 | 1,927 |
Level 3 | | |
Investments, Debt and Equity Securities [Abstract] | | |
Total investment securities | 4 | 6 |
Fair Value, Measurements, Recurring | | |
Assets | | |
Cash equivalents in mutual funds | 34 | 41 |
Cash equivalents in securities | | 6 |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 1,700 | 1,907 |
Other securities | 73 | 85 |
Total investment securities | 1,773 | 1,992 |
Restricted cash equivalents in mutual funds | 525 | 468 |
Total | 2,332 | 2,507 |
Fair Value, Measurements, Recurring | Total bonds | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 25 | 30 |
Fair Value, Measurements, Recurring | U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 13 | 16 |
Fair Value, Measurements, Recurring | Obligations of states, municipalities, and political subdivisions | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 69 | 79 |
Fair Value, Measurements, Recurring | Commercial paper | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 58 | 50 |
Fair Value, Measurements, Recurring | Non-U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 137 | 155 |
Fair Value, Measurements, Recurring | Corporate debt | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 1,122 | 1,302 |
Other securities | 8 | 9 |
Fair Value, Measurements, Recurring | RMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 175 | 170 |
Other securities | 1 | 1 |
Fair Value, Measurements, Recurring | CMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 39 | 45 |
Fair Value, Measurements, Recurring | CDO/ABS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 87 | 90 |
Other securities | 16 | 20 |
Fair Value, Measurements, Recurring | Preferred stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 17 | 22 |
Fair Value, Measurements, Recurring | Common stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 31 | 33 |
Fair Value, Measurements, Recurring | Level 1 | | |
Assets | | |
Cash equivalents in mutual funds | 34 | 41 |
Cash equivalents in securities | | 0 |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 4 | 5 |
Other securities | 47 | 54 |
Total investment securities | 51 | 59 |
Restricted cash equivalents in mutual funds | 525 | 468 |
Total | 610 | 568 |
Fair Value, Measurements, Recurring | Level 1 | Total bonds | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | Obligations of states, municipalities, and political subdivisions | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | Commercial paper | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | Non-U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | Corporate debt | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 4 | 5 |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | RMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | CMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | CDO/ABS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 1 | Preferred stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 17 | 22 |
Fair Value, Measurements, Recurring | Level 1 | Common stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 30 | 32 |
Fair Value, Measurements, Recurring | Level 2 | | |
Assets | | |
Cash equivalents in mutual funds | 0 | 0 |
Cash equivalents in securities | | 6 |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 1,693 | 1,897 |
Other securities | 25 | 30 |
Total investment securities | 1,718 | 1,927 |
Restricted cash equivalents in mutual funds | 0 | 0 |
Total | 1,718 | 1,933 |
Fair Value, Measurements, Recurring | Level 2 | Total bonds | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 25 | 30 |
Fair Value, Measurements, Recurring | Level 2 | U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 13 | 16 |
Fair Value, Measurements, Recurring | Level 2 | Obligations of states, municipalities, and political subdivisions | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 69 | 79 |
Fair Value, Measurements, Recurring | Level 2 | Commercial paper | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 58 | 50 |
Fair Value, Measurements, Recurring | Level 2 | Non-U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 137 | 155 |
Fair Value, Measurements, Recurring | Level 2 | Corporate debt | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 1,115 | 1,292 |
Other securities | 8 | 9 |
Fair Value, Measurements, Recurring | Level 2 | RMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 175 | 170 |
Other securities | 1 | 1 |
Fair Value, Measurements, Recurring | Level 2 | CMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 39 | 45 |
Fair Value, Measurements, Recurring | Level 2 | CDO/ABS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 87 | 90 |
Other securities | 16 | 20 |
Fair Value, Measurements, Recurring | Level 2 | Preferred stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 2 | Common stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | | |
Assets | | |
Cash equivalents in mutual funds | 0 | 0 |
Cash equivalents in securities | | 0 |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 3 | 5 |
Other securities | 1 | 1 |
Total investment securities | 4 | 6 |
Restricted cash equivalents in mutual funds | 0 | 0 |
Total | 4 | 6 |
Fair Value, Measurements, Recurring | Level 3 | Total bonds | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | Obligations of states, municipalities, and political subdivisions | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | Commercial paper | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | Non-U.S. government and government sponsored entities | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | Corporate debt | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 3 | 5 |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | RMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | CMBS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | CDO/ABS | | |
Investments, Debt and Equity Securities [Abstract] | | |
Available-for-sale securities | 0 | 0 |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | Preferred stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | 0 | 0 |
Fair Value, Measurements, Recurring | Level 3 | Common stock | | |
Investments, Debt and Equity Securities [Abstract] | | |
Other securities | $ 1 | $ 1 |