Defined Benefit Postretirement Plans and Defined Contribution Plan - Fair Value of Defined Benefit Pension Plan Assets (Details) - Recurring - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 192	$ 194
Plan assets before comingled funds	50	87
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	(1)
Common stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets	28	61
Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	7	8
Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16	18
Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	142	107
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	27	61
Plan assets before comingled funds	27	61
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	(1)
Level 1 | Common stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets	28	61
Level 1 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 1 | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Plan assets before comingled funds	0	0
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Level 2 | Common stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 2 | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	23	26
Plan assets before comingled funds	23	26
Level 3 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Level 3 | Common stock
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	7	8
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	16	18
Level 3 | Commingled funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 0	$ 0