Benefit Obligations (Schedule of Fair Values of Pension Plan Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets, fair value non-financial receivables		$ 29	$ 36
Pension plan assets, fair value non-financial payables		26	19
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[1]	2,352	2,220
Total liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(7)	(3)
Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(7)	(3)
Defined Benefit Plan, Equity Securities, Non-US [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		77	59
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		8	2
Total plan assets [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[2]	2,359	2,223
Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		689	595
Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		7	3
Corporate Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		762	691
Treasuries, Other Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		1,438	1,420
Mortgage Backed Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		15	8
Registered Investment Companies [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		62	54
Short-term Investments [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		35	29
Insurance Contracts [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		47	35
Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		5	5
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[1]	124	192
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Total liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Defined Benefit Plan, Equity Securities, Non-US [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		77	59
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		8	2
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Total plan assets [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[2]	124	192
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Treasuries, Other Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		35	127
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Mortgage Backed Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Insurance Contracts [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		4	4
Significant Other Observable Inputs (Level 2) [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[1]	2,228	2,028
Significant Other Observable Inputs (Level 2) [Member] | Total liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(7)	(3)
Significant Other Observable Inputs (Level 2) [Member] | Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(7)	(3)
Significant Other Observable Inputs (Level 2) [Member] | Defined Benefit Plan, Equity Securities, Non-US [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Significant Other Observable Inputs (Level 2) [Member] | Defined Benefit Plan, Cash and Cash Equivalents [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		0	0
Significant Other Observable Inputs (Level 2) [Member] | Total plan assets [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[2]	2,235	2,031
Significant Other Observable Inputs (Level 2) [Member] | Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		7	3
Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		762	691
Significant Other Observable Inputs (Level 2) [Member] | Treasuries, Other Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		1,403	1,293
Significant Other Observable Inputs (Level 2) [Member] | Mortgage Backed Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		15	8
Significant Other Observable Inputs (Level 2) [Member] | Insurance Contracts [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		47	35
Significant Other Observable Inputs (Level 2) [Member] | Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		$ 1	$ 1

[1] Total net assets excludes non-financial plan receivables and payables of $29 million and $26 million, respectively, as of December 31, 2019 and $36 million and $19 million, respectively, as of December 31, 2018. Non-financial items include due to/from broker, interest receivables and accrued expenses.

[2] Certain investments that are measured at fair value using the NAV per share practical expedient have not been classified in the fair value hierarchy. Total investments, at fair value, for the year ended December 31, 2019 excludes investments in common/collective trusts, registered investment companies and short-term investment funds with fair values of $689 million, $62 million and $35 million, respectively. Total investments, at fair value, for the year ended December 31, 2018 excludes investments in common/collective trusts, registered investment companies and short-term investment funds with fair values of $595 million, $54 million and $29 million, respectively.