Fair Value Measurements - Assets at Fair Value Recurring Basis (Details) - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | $ 1,647 | $ 1,729 | |
Other securities | | 72 | 71 | |
Restricted cash and restricted cash equivalents | [1] | 534 | 461 | $ 476 |
U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 17 | 16 | |
Obligations of states, municipalities, and political subdivisions | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 66 | 66 | |
Corporate debt | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 1,085 | 1,137 | |
RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 180 | 192 | |
CMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 33 | 35 | |
CDO/ABS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 85 | 86 | |
Level 1 | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Total investment securities | | 54 | 51 | |
Restricted cash and restricted cash equivalents | | 534 | 450 | |
Level 2 | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Total investment securities | | 1,662 | 1,744 | |
Restricted cash and restricted cash equivalents | | 0 | 11 | |
Level 3 | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Total investment securities | | 3 | 5 | |
Restricted cash and restricted cash equivalents | | 0 | 0 | |
Fair Value, Measurements, Recurring | | | | |
Assets | | | | |
Cash equivalents in mutual funds | | 97 | 77 | |
Cash equivalents in securities | | | 17 | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 1,647 | 1,729 | |
Other securities | | 72 | 71 | |
Total investment securities | | 1,719 | 1,800 | |
Restricted cash equivalents in mutual funds | | 525 | 445 | |
Restricted cash and restricted cash equivalents | | | 11 | |
Total | | 2,341 | 2,350 | |
Fair Value, Measurements, Recurring | Total bonds | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | | 22 | 23 | |
Fair Value, Measurements, Recurring | U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 17 | 16 | |
Fair Value, Measurements, Recurring | Obligations of states, municipalities, and political subdivisions | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 66 | 66 | |
Fair Value, Measurements, Recurring | Commercial paper | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 14 | 55 | |
Fair Value, Measurements, Recurring | Non-U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 167 | 142 | |
Fair Value, Measurements, Recurring | Corporate debt | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 1,085 | 1,137 | |
Other securities | | 4 | 6 | |
Fair Value, Measurements, Recurring | RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 180 | 192 | |
Other securities | | | 1 | |
Fair Value, Measurements, Recurring | CMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 33 | 35 | |
Fair Value, Measurements, Recurring | CDO/ABS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 85 | 86 | |
Other securities | | 18 | 16 | |
Fair Value, Measurements, Recurring | Preferred stock | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | | 16 | 15 | |
Fair Value, Measurements, Recurring | Common stock | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | | 34 | 33 | |
Fair Value, Measurements, Recurring | Level 1 | | | | |
Assets | | | | |
Cash equivalents in mutual funds | | 97 | 77 | |
Cash equivalents in securities | | | 0 | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 6 | 5 | |
Other securities | | 48 | 46 | |
Total investment securities | | 54 | 51 | |
Restricted cash equivalents in mutual funds | | 525 | 445 | |
Restricted cash and restricted cash equivalents | | | 0 | |
Total | | 676 | 573 | |
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 | | 6 | 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 | |
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 | | 16 | 15 | |
Fair Value, Measurements, Recurring | Level 1 | Common stock | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | | 32 | 31 | |
Fair Value, Measurements, Recurring | Level 2 | | | | |
Assets | | | | |
Cash equivalents in mutual funds | | 0 | 0 | |
Cash equivalents in securities | | | 17 | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 1,640 | 1,721 | |
Other securities | | 22 | 23 | |
Total investment securities | | 1,662 | 1,744 | |
Restricted cash equivalents in mutual funds | | 0 | 0 | |
Restricted cash and restricted cash equivalents | | | 11 | |
Total | | 1,662 | 1,772 | |
Fair Value, Measurements, Recurring | Level 2 | Total bonds | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | | 22 | 23 | |
Fair Value, Measurements, Recurring | Level 2 | U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 17 | 16 | |
Fair Value, Measurements, Recurring | Level 2 | Obligations of states, municipalities, and political subdivisions | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 66 | 66 | |
Fair Value, Measurements, Recurring | Level 2 | Commercial paper | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 14 | 55 | |
Fair Value, Measurements, Recurring | Level 2 | Non-U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 167 | 142 | |
Fair Value, Measurements, Recurring | Level 2 | Corporate debt | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 1,078 | 1,129 | |
Other securities | | 4 | 6 | |
Fair Value, Measurements, Recurring | Level 2 | RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 180 | 192 | |
Other securities | | | 1 | |
Fair Value, Measurements, Recurring | Level 2 | CMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 33 | 35 | |
Fair Value, Measurements, Recurring | Level 2 | CDO/ABS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | | 85 | 86 | |
Other securities | | 18 | 16 | |
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 | | 1 | 3 | |
Other securities | | 2 | 2 | |
Total investment securities | | 3 | 5 | |
Restricted cash equivalents in mutual funds | | 0 | 0 | |
Restricted cash and restricted cash equivalents | | | 0 | |
Total | | 3 | 5 | |
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 | | 1 | 3 | |
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 | |
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 | | $ 2 | $ 2 | |
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[1] Restricted cash and restricted cash equivalents primarily represent funds required to be used for future debt payments relating to our secured transactions. | |