Pension and Postretirement Benefit Plans - Fair Value of Pension Plan Assets (Details) - Pension Plan [Member] - USD ($) $ in Millions		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 1,372		$ 1,584
UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,301		1,513		$ 1,454
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		71		71		51
Fair Value, Inputs, Level 1 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		39		69
Fair Value, Inputs, Level 1 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0		0
Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		883		911
Fair Value, Inputs, Level 2 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		36		38
Fair Value, Inputs, Level 3 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		35		33
Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	379		533
Defined Benefit Plan, Equity Securities, US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	35		62
Defined Benefit Plan, Equity Securities, US [Member] | Fair Value, Inputs, Level 1 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[2]	35		62
Defined Benefit Plan, Equity Securities, US, Large Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43		61
Defined Benefit Plan, Equity Securities, US, Large Cap [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	43		61
Defined Benefit Plan, Equity Securities, US, Small Cap [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4		7
Defined Benefit Plan, Equity Securities, US, Small Cap [Member] | Fair Value, Inputs, Level 1 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		4		7
Defined Benefit Plan, Equity Securities, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		41		65
Defined Benefit Plan, Equity Securities, Non-US [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	41		65
Defined Benefit Plan, Equity Securities, Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		28		52
Defined Benefit Plan, Equity Securities, Emerging Markets [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Defined Benefit Plan, Equity Securities, Emerging Markets [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	28		52
Defined Benefit Plan, Debt Security [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	33		61
Defined Benefit Plan, Debt Security [Member] | Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[3]	33		61
Defined Benefit Plan, Debt Security [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1],[3]
Corporate Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		814		464
Corporate Debt Securities [Member] | Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		616		226
Corporate Debt Securities [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	198		238
US Treasury Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		115		281
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		115		281
Debt Security, Government, Non-US [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		25		26
Debt Security, Government, Non-US [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		25		26
Defined Benefit Plan, Fixed Income Securities, Emerging Markets [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		48		82
Defined Benefit Plan, Fixed Income Securities, Emerging Markets [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	48		82
Insurance Contracts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[4]	35		33
Insurance Contracts [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		35	[4]	33	[4]	$ 16
Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		21		35
Real Estate [Member] | Fair Value Measured at Net Asset Value Per Share [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	21		35
Other Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[5]	10		1
Other Securities [Member] | Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[5]			(10)
Other Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[5]	10		11
Other Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[5]
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		120		354
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		119		353
Cash and Cash Equivalents [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 1		1
Interest Rate Contract [Member] | Fair Value, Inputs, Level 2 [Member] | UNITED STATES
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Plan Assets, Investment within Plan Asset Category, Amount	[5]			$ (10)

[1] Certain assets are measured at fair value using the net asset value (NAV) per share (or its equivalent) practical expedient and have not been classified in the fair value hierarchy.

[2] This category comprises a combination of small-, mid- and large-cap equity stocks that are allocated at the investment manager's discretion. Investments include common and preferred securities as well as equity funds that invest in these instruments.

[3] This category represents a combination of high-yield and investment grade corporate bonds, sovereign bonds, Yankee bonds, asset-backed securities and U.S. government bonds. Investments include fixed income funds that invest in these instruments.

[4] This category comprises contracts placed with insurance companies where the underlying assets are invested in fixed interest securities.

[5] Other assets in the U.S. represent interest rate derivatives which had a market value of $(10) at December 31, 2017.