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, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Percent of fixed income assets invested in US treasury or agency securities	50.00%	50.00%
Other Retiree Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 54	$ 0	$ 0
Other Retiree Benefit Plans | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36	0
Other Retiree Benefit Plans | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18	0
Other Retiree Benefit Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	0
Other Retiree Benefit Plans | U.S. common stocks | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	0
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	4	0
Other Retiree Benefit Plans | Fixed income securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	28	0
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	8	0
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	4	0
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	2	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	3	0
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	1	0
Other Retiree Benefit Plans | Other assets and liabilities, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,568	1,812	1,646
United States | Pension Plans | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,076	1,130
United States | Pension Plans | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	534	707
United States | Pension Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29	21
United States | Pension Plans | U.S. common stocks | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	75	127
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	106	138
United States | Pension Plans | Fixed income securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	865	843
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	229	350
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	116	122
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	56	82
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	94	115
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	39	38
United States | Pension Plans | Other assets and liabilities, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(42)	(25)
International | Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	510	575	$ 509
International | Pension Plans | Fair Value, Inputs, Level 1, 2 and 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	173	189
International | Pension Plans | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	337	386
International | Pension Plans | Cash and cash equivalents | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9	11
International | Pension Plans | U.S. common stocks | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3	4
International | Pension Plans | International common stocks | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	3
International | Pension Plans | Pooled funds | Fair Value, Inputs, Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	82	94
International | Pension Plans | Fixed income securities | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	24	24
International | Pension Plans | Guaranteed investment contracts | Fair Value, Inputs, Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51	53
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	134	189
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	173	167
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	5
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	3
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	22	22
International | Pension Plans | Other assets and liabilities, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0	$ 0