Fair Value Measurements - Schedule of Fair Value of Investment Assets (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	$ 144	$ 181
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Amortized Cost	144	184
Level 1 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	2	80
Level 1 | Fair Value | Fixed Income Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	80
Level 1 | Fair Value | Exchange-traded Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	2	0
Level 1 | Fair Value | Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	0
Level 1 | Fair Value | Asset-backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	0
Level 1 | Fair Value | Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	0
Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	144	101
Level 2 | Fair Value | Fixed Income Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	0
Level 2 | Fair Value | Exchange-traded Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	0
Level 2 | Fair Value | Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	76	60
Level 2 | Fair Value | Asset-backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	28	1
Level 2 | Fair Value | Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	40	40
Total | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	146	181
Total | Fair Value | Fixed Income Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	0	80
Total | Fair Value | Exchange-traded Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	2	0
Total | Fair Value | Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	76	60
Total | Fair Value | Asset-backed Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	28	1
Total | Fair Value | Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total Investments at Fair Value	$ 40	$ 40