Fair Value Measurements - Fair Value of Investment Assets (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	$ 174	$ 164
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total investments at amortized cost	172		$ 156
Level 1 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	87		75
Level 1 | Fair Value | Fixed Income Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	87		75
Level 1 | Fair Value | Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	0		0
Level 1 | Fair Value | Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	0		0
Level 1 | Fair Value | Commercial Paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	0		0
Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	87		89
Level 2 | Fair Value | Fixed Income Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	0		0
Level 2 | Fair Value | Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	58		63
Level 2 | Fair Value | Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	23		26
Level 2 | Fair Value | Commercial Paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	6		0
Total | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	174		164
Total | Fair Value | Fixed Income Mutual Funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	87		75
Total | Fair Value | Corporate Bonds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	58		63
Total | Fair Value | Government Securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	23		26
Total | Fair Value | Commercial Paper
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commercial Paper	$ 6		$ 0