Fair Value Measurements - Assets at Fair Value Recurring Basis (Details) - USD ($) $ in Millions | Jun. 30, 2024 | Dec. 31, 2023 | Jun. 30, 2023 | [1] |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | $ 1,611 | | $ 1,647 | |
Other securities | 70 | | 72 | |
Restricted cash and restricted cash equivalents | 630 | [1] | 534 | $ 532 |
U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 12 | | 17 | |
Obligations of states, municipalities, and political subdivisions | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 65 | | 66 | |
Commercial paper | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 40 | | 14 | |
Non-U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 161 | | 167 | |
Corporate debt | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 1,059 | | 1,085 | |
RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 175 | | 180 | |
CMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 26 | | 33 | |
CDO/ABS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 73 | | 85 | |
Level 1 | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Total investment securities | 53 | | 54 | |
Restricted cash and restricted cash equivalents | 629 | | 534 | |
Level 2 | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Total investment securities | 1,624 | | 1,662 | |
Restricted cash and restricted cash equivalents | 1 | | 0 | |
Level 3 | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Total investment securities | 4 | | 3 | |
Restricted cash and restricted cash equivalents | 0 | | 0 | |
Fair Value, Measurements, Recurring | | | | |
Assets | | | | |
Cash equivalents in mutual funds | 164 | | 97 | |
Cash equivalents in securities | 48 | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 1,611 | | 1,647 | |
Other securities | 70 | | 72 | |
Total investment securities | 1,681 | | 1,719 | |
Restricted cash equivalents in mutual funds | 623 | | 525 | |
Restricted cash and restricted cash equivalents | 1 | | | |
Total | 2,517 | | 2,341 | |
Fair Value, Measurements, Recurring | Total bonds | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | 21 | | 22 | |
Fair Value, Measurements, Recurring | U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 12 | | 17 | |
Fair Value, Measurements, Recurring | Obligations of states, municipalities, and political subdivisions | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 65 | | 66 | |
Fair Value, Measurements, Recurring | Commercial paper | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 40 | | 14 | |
Fair Value, Measurements, Recurring | Non-U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 161 | | 167 | |
Fair Value, Measurements, Recurring | Corporate debt | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 1,059 | | 1,085 | |
Other securities | 5 | | 4 | |
Fair Value, Measurements, Recurring | RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 175 | | 180 | |
Fair Value, Measurements, Recurring | CMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 26 | | 33 | |
Fair Value, Measurements, Recurring | CDO/ABS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 73 | | 85 | |
Other securities | 16 | | 18 | |
Fair Value, Measurements, Recurring | Preferred stock | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | 14 | | 16 | |
Fair Value, Measurements, Recurring | Common stock | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | 35 | | 34 | |
Fair Value, Measurements, Recurring | Level 1 | | | | |
Assets | | | | |
Cash equivalents in mutual funds | 164 | | 97 | |
Cash equivalents in securities | 0 | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 6 | | 6 | |
Other securities | 47 | | 48 | |
Total investment securities | 53 | | 54 | |
Restricted cash equivalents in mutual funds | 623 | | 525 | |
Restricted cash and restricted cash equivalents | 0 | | | |
Total | 840 | | 676 | |
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 | | 6 | |
Other securities | 0 | | 0 | |
Fair Value, Measurements, Recurring | Level 1 | RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale 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 | 14 | | 16 | |
Fair Value, Measurements, Recurring | Level 1 | Common stock | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | 33 | | 32 | |
Fair Value, Measurements, Recurring | Level 2 | | | | |
Assets | | | | |
Cash equivalents in mutual funds | 0 | | 0 | |
Cash equivalents in securities | 48 | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 1,604 | | 1,640 | |
Other securities | 20 | | 22 | |
Total investment securities | 1,624 | | 1,662 | |
Restricted cash equivalents in mutual funds | 0 | | 0 | |
Total | 1,673 | | 1,662 | |
Fair Value, Measurements, Recurring | Level 2 | Total bonds | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | 20 | | 22 | |
Fair Value, Measurements, Recurring | Level 2 | U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 12 | | 17 | |
Fair Value, Measurements, Recurring | Level 2 | Obligations of states, municipalities, and political subdivisions | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 65 | | 66 | |
Fair Value, Measurements, Recurring | Level 2 | Commercial paper | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 40 | | 14 | |
Fair Value, Measurements, Recurring | Level 2 | Non-U.S. government and government sponsored entities | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 161 | | 167 | |
Fair Value, Measurements, Recurring | Level 2 | Corporate debt | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 1,052 | | 1,078 | |
Other securities | 4 | | 4 | |
Fair Value, Measurements, Recurring | Level 2 | RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 175 | | 180 | |
Fair Value, Measurements, Recurring | Level 2 | CMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 26 | | 33 | |
Fair Value, Measurements, Recurring | Level 2 | CDO/ABS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale securities | 73 | | 85 | |
Other securities | 16 | | 18 | |
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 | | 1 | |
Other securities | 3 | | 2 | |
Total investment securities | 4 | | 3 | |
Restricted cash equivalents in mutual funds | 0 | | 0 | |
Restricted cash and restricted cash equivalents | 0 | | | |
Total | 4 | | 3 | |
Fair Value, Measurements, Recurring | Level 3 | Total bonds | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Other securities | 1 | | 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 | | 1 | |
Other securities | 1 | | 0 | |
Fair Value, Measurements, Recurring | Level 3 | RMBS | | | | |
Investments, Debt and Equity Securities [Abstract] | | | | |
Available-for-sale 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 | $ 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. |