Retirement Plans and Other Retiree Benefits - Allocation of Plan Assets and Level of Valuation Input, by Major Asset Category (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 |
Defined Benefit Plan Disclosure [Line Items] | | | |
Percent of fixed income assets invested in US treasury or agency securities | 50.00% | 50.00% | |
Other assets and liabilities, net | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | | $ 0 | |
Other Retiree Benefit Plans | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | $ 3 | 37 | $ 54 |
Other Retiree Benefit Plans | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 2 | 24 | |
Other Retiree Benefit Plans | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1 | 13 | |
Other Retiree Benefit Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 1 | |
Other Retiree Benefit Plans | U.S. common stocks | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 1 | |
Other Retiree Benefit Plans | International common stocks | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 0 | |
Other Retiree Benefit Plans | Pooled funds | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 2 | |
Other Retiree Benefit Plans | Fixed income securities | Fair Value, Inputs, Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 2 | 20 | |
Other Retiree Benefit Plans | Guaranteed investment contracts | Fair Value, Inputs, Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 0 | |
Other Retiree Benefit Plans | Domestic, developed and emerging markets equity funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1 | 7 | |
Other Retiree Benefit Plans | Fixed income funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 3 | |
Other Retiree Benefit Plans | Hedge funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 0 | |
Other Retiree Benefit Plans | Multi-Asset funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 2 | |
Other Retiree Benefit Plans | Real estate funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 1 | |
Other Retiree Benefit Plans | Other assets and liabilities, net | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | | |
United States | Pension Plans | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1,921 | 1,806 | 1,568 |
United States | Pension Plans | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1,233 | 1,187 | |
United States | Pension Plans | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 703 | 704 | |
United States | Pension Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 50 | 41 | |
United States | Pension Plans | U.S. common stocks | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 49 | |
United States | Pension Plans | International common stocks | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 0 | |
United States | Pension Plans | Pooled funds | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 65 | 29 | |
United States | Pension Plans | Fixed income securities | Fair Value, Inputs, Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1,117 | 1,067 | |
United States | Pension Plans | Guaranteed investment contracts | Fair Value, Inputs, Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1 | 1 | |
United States | Pension Plans | Domestic, developed and emerging markets equity funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 456 | 328 | |
United States | Pension Plans | Fixed income funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 136 | 177 | |
United States | Pension Plans | Hedge funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 0 | 3 | |
United States | Pension Plans | Multi-Asset funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 77 | 155 | |
United States | Pension Plans | Real estate funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 34 | 41 | |
United States | Pension Plans | Other assets and liabilities, net | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | (15) | (85) | |
International | Pension Plans | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 698 | 586 | $ 510 |
International | Pension Plans | Fair Value, Inputs, Level 1, 2 and 3 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 252 | 181 | |
International | Pension Plans | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 446 | 405 | |
International | Pension Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 12 | 15 | |
International | Pension Plans | U.S. common stocks | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 1 | 3 | |
International | Pension Plans | International common stocks | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 8 | 3 | |
International | Pension Plans | Pooled funds | Fair Value, Inputs, Level 1 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 117 | 104 | |
International | Pension Plans | Fixed income securities | Fair Value, Inputs, Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 59 | 14 | |
International | Pension Plans | Guaranteed investment contracts | Fair Value, Inputs, Level 2 | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 55 | 42 | |
International | Pension Plans | Domestic, developed and emerging markets equity funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 183 | 165 | |
International | Pension Plans | Fixed income funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 225 | 196 | |
International | Pension Plans | Hedge funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 6 | 17 | |
International | Pension Plans | Multi-Asset funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 2 | 2 | |
International | Pension Plans | Real estate funds | Fair Value Measured at Net Asset Value Per Share | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | 30 | 25 | |
International | Pension Plans | Other assets and liabilities, net | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Fair value of plan assets | $ 0 | $ 0 | |