Benefit Obligations (Schedule of Fair Values of Pension Plan Assets) (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Pension plan assets, fair value non-financial receivables		$ 72	$ 29
Pension plan assets, fair value non-financial payables		67	26
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[1]	2,535	2,352
Total liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(3)	(7)
Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(3)	(7)
Defined Benefit Plan, Equity Securities, Non-US [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		82	77
Defined Benefit Plan, Cash and Cash Equivalents [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		10	8
Total plan assets [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets	[2]	2,538	2,359
Equities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		732	689
Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		3	7
Corporate Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		890	762
Treasuries, Other Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		1,464	1,438
Mortgage Backed Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		16	15
Registered Investment Companies [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		71	62
Short-term Investments [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		45	35
Insurance Contracts [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		63	47
Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		10	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]	113	124
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		82	77
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		10	8
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]	113	124
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		17	35
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]	2,422	2,228
Significant Other Observable Inputs (Level 2) [Member] | Total liabilities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(3)	(7)
Significant Other Observable Inputs (Level 2) [Member] | Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		(3)	(7)
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]	2,425	2,235
Significant Other Observable Inputs (Level 2) [Member] | Swaps [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		3	7
Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		890	762
Significant Other Observable Inputs (Level 2) [Member] | Treasuries, Other Debt [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		1,447	1,403
Significant Other Observable Inputs (Level 2) [Member] | Mortgage Backed Securities [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		16	15
Significant Other Observable Inputs (Level 2) [Member] | Insurance Contracts [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		63	47
Significant Other Observable Inputs (Level 2) [Member] | Other [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Total net assets		$ 6	$ 1

[1] Total net assets excludes non-financial plan receivables and payables of $72 million and $67 million, respectively, as of December 31, 2020 and $29 million and $26 million, respectively, as of December 31, 2019. 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, 2020 excludes investments in common/collective trusts, registered investment companies and short-term investment funds with fair values of $732 million, $71 million and $45 million, respectively. 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.