Pension and Postretirement Plans (Summary of Pension Plan Asset Fair Values) (Details) - Pension Benefits - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
United States
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 2,702	$ 2,377	$ 2,751
Subtotal	1,182	1,210
United States | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,048	1,081
Subtotal	1,048	1,081
United States | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134	129
Subtotal	134	129
United States | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Subtotal	0	0
United States | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	437	421
United States | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	437	421
United States | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Government debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	475	610
United States | Government debt securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	475	610
United States | Government debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Government debt securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134	129
United States | Corporate debt securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Corporate debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134	129
United States | Corporate debt securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	136	50
United States | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	136	50
United States | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Insurance contracts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Insurance contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Insurance contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
United States | Common/collective trusts measured at NAV | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
United States | Common/collective trusts measured at NAV | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
United States | Common/collective trusts measured at NAV | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
United States | Common/collective trusts measured at NAV | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,364	1,048
United States | Real estate funds measured at NAV | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
United States | Real estate funds measured at NAV | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
United States | Real estate funds measured at NAV | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
United States | Real estate funds measured at NAV | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	156	119
Int’l.
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,046	902	$ 972
Subtotal	18	21
Int’l. | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	7
Subtotal	4	7
Int’l. | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Subtotal	0	0
Int’l. | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Subtotal	14	14
Int’l. | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Government debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Government debt securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Government debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Government debt securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Corporate debt securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Corporate debt securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Corporate debt securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Corporate debt securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	7
Int’l. | Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4	7
Int’l. | Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Cash and cash equivalents | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Int’l. | Insurance contracts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Insurance contracts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Int’l. | Insurance contracts | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14	14
Int’l. | Common/collective trusts measured at NAV | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Int’l. | Common/collective trusts measured at NAV | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Int’l. | Common/collective trusts measured at NAV | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets
Int’l. | Common/collective trusts measured at NAV | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	938	873
Int’l. | Real estate funds measured at NAV | Fair Value Measured at Net Asset Value Per Share
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 90	$ 8