Employee Benefits - Fair Values of Pension Plan Assets by Asset Category (Details) - Pension Plan - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 1,096	$ 1,153	$ 1,102
Fair Value, Inputs, Level 1, 2 and 3 | Fixed income — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets	454
Fair Value, Inputs, Level 1, 2 and 3 | Common — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		9
Fair Value, Inputs, Level 1, 2 and 3 | Preferred — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		3
Fair Value, Inputs, Level 1, 2 and 3 | Corporate bonds — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		171
Fair Value, Inputs, Level 1, 2 and 3 | Corporate bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		79
Fair Value, Inputs, Level 1, 2 and 3 | U.S. Treasury, agencies and corporations
Defined Benefit Plan Disclosure [Line Items]
Plan assets		165
Fair Value, Inputs, Level 1, 2 and 3 | Government bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		2
Fair Value, Inputs, Level 1, 2 and 3 | States and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Plan assets		27
Fair Value, Inputs, Level 1, 2 and 3 | Equity - International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		2
Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	14
Level 1 | Fixed income — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Level 1 | Common — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		9
Level 1 | Preferred — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		3
Level 1 | Corporate bonds — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 1 | Corporate bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 1 | U.S. Treasury, agencies and corporations
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 1 | Government bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 1 | States and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 1 | Equity - International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	454	444
Level 2 | Fixed income — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets	454
Level 2 | Common — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 2 | Preferred — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 2 | Corporate bonds — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		171
Level 2 | Corporate bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		79
Level 2 | U.S. Treasury, agencies and corporations
Defined Benefit Plan Disclosure [Line Items]
Plan assets		165
Level 2 | Government bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		2
Level 2 | States and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Plan assets		27
Level 2 | Equity - International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Level 3 | Fixed income — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0
Level 3 | Common — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | Preferred — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | Corporate bonds — U.S.
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | Corporate bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | U.S. Treasury, agencies and corporations
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | Government bonds — International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | States and political subdivisions
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Level 3 | Equity - International
Defined Benefit Plan Disclosure [Line Items]
Plan assets		0
Measured at NAV | Collective Investment Funds (measured at NAV)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	622	636
Measured at NAV | Insurance investment contracts and pooled separate accounts (measured at NAV)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	19	17
Measured at NAV | Other assets (measured at NAV)
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 1	$ 42