Employee Benefits - Fair Value of Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	$ 2,231	$ 2,243
Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	1,572	1,566
Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	12	54
Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	1,516	1,474
Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	44	38
Common collective trust funds measured at net asset value as a practical expedient
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	659	677
Cash and short-term investments | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	6	4
Cash and short-term investments | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	6	4
Cash and short-term investments | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Cash and short-term investments | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
U.S. indexes | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	6	9
U.S. indexes | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	6	9
U.S. indexes | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
U.S. indexes | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
U.S. growth and value | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets		41
U.S. growth and value | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets		41
U.S. growth and value | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets		0
U.S. growth and value | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets		0
Long duration strategy | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	1,376	1,339
Long duration strategy | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Long duration strategy | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	1,376	1,339
Long duration strategy | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Intermediate duration securities | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	59	57
Intermediate duration securities | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Intermediate duration securities | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	59	57
Intermediate duration securities | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Real Estate: U.K. | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	44	38
Real Estate: U.K. | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Real Estate: U.K. | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Real Estate: U.K. | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	44	38
Infrastructure: U.K. | Total
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	81	78
Infrastructure: U.K. | Level 1
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	0	0
Infrastructure: U.K. | Level 2
Fair value of defined benefit plans assets by asset class
Fair value of plan assets	81	78
Infrastructure: U.K. | Level 3
Fair value of defined benefit plans assets by asset class
Fair value of plan assets		$ 0