Pension and Other Postretirement Benefits - Schedule of Fair Value of Pension Plan Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net payables which represents assets related to divested businesses to be transferred to the buyers	$ 76
Net receivables which represents assets related to divested businesses to be transferred to the buyers		$ 7
Pension benefits paid
Defined Benefit Plan Disclosure [Line Items]
Net plan assets	1,724	4,868	$ 4,334
Net plan assets excluding certain net receivables	1,800	4,875
Pension benefits paid | Equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	595	1,513
Pension benefits paid | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	431	1,098
Pension benefits paid | Long/short equity hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	77	260
Pension benefits paid | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	87	155
Pension benefits paid | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	1,005	2,448
Pension benefits paid | Intermediate and long duration government/credit
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	688	2,171
Pension benefits paid | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	317	277
Pension benefits paid | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	200	914
Pension benefits paid | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	83	269
Pension benefits paid | Discretionary and systematic macro hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	94	405
Pension benefits paid | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	23	240
Pension benefits paid | Level 1
Defined Benefit Plan Disclosure [Line Items]
Net plan assets	446	941
Pension benefits paid | Level 1 | Equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	274	590
Pension benefits paid | Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	274	590
Pension benefits paid | Level 1 | Long/short equity hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 1 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 1 | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	141	247
Pension benefits paid | Level 1 | Intermediate and long duration government/credit
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	78	121
Pension benefits paid | Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	63	126
Pension benefits paid | Level 1 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	31	104
Pension benefits paid | Level 1 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	31	104
Pension benefits paid | Level 1 | Discretionary and systematic macro hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 2
Defined Benefit Plan Disclosure [Line Items]
Net plan assets	922	1,054
Pension benefits paid | Level 2 | Equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	89	0
Pension benefits paid | Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	89	0
Pension benefits paid | Level 2 | Long/short equity hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 2 | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 2 | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	833	1,054
Pension benefits paid | Level 2 | Intermediate and long duration government/credit
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	579	1,047
Pension benefits paid | Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	254	7
Pension benefits paid | Level 2 | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 2 | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 2 | Discretionary and systematic macro hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	0
Pension benefits paid | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Net plan assets	432	2,880
Pension benefits paid | Net Asset Value | Equities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	232	923
Pension benefits paid | Net Asset Value | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	68	508
Pension benefits paid | Net Asset Value | Long/short equity hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	77	260
Pension benefits paid | Net Asset Value | Private equity
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	87	155
Pension benefits paid | Net Asset Value | Fixed income
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	31	1,147
Pension benefits paid | Net Asset Value | Intermediate and long duration government/credit
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	31	1,003
Pension benefits paid | Net Asset Value | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	0	144
Pension benefits paid | Net Asset Value | Other investments
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	169	810
Pension benefits paid | Net Asset Value | Real estate
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	52	165
Pension benefits paid | Net Asset Value | Discretionary and systematic macro hedge funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	94	405
Pension benefits paid | Net Asset Value | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	$ 23	$ 240