Fair Value Measurements - Schedule of Pension Plan Assets at Fair Value by Level (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	$ 2,825	$ 2,431
Total investments in the fair value hierarchy	1,952	1,461
Common Stock
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	823	750
Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	78	7
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	229	3
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	588	537
Government securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	217	149
Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	8	10
Derivatives and other
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	9	5
Level 1
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	1,130	760
Total investments in the fair value hierarchy	1,130	760
Level 1 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	823	750
Level 1 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	78	7
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	229	3
Level 1 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 | Government securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 1 | Derivatives and other
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	822	701
Total investments in the fair value hierarchy	822	701
Level 2 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 | Mutual funds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	0	0
Level 2 | Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	588	537
Level 2 | Government securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	217	149
Level 2 | Asset-backed securities
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	8	10
Level 2 | Derivatives and other
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets at fair value	9	5
Investments measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Investments measured at net asset value	$ 873	$ 970