Fair Value Measurements (Schedule of Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities without Readily Determinable Fair Value, Amount	$ 170	$ 164
Equity Securities, FV-NI and without Readily Determinable Fair Value	0	0
Insurance contracts in nonqualified trusts, carrying amount	35	37
Insurance contracts in nonqualified trusts, fair value	35	37
Long-term debt, including current installments of long-term debt, carrying amount	3,313	3,355
Long-term debt, including current installments of long-term debt, fair value	3,390	3,371
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI and without Readily Determinable Fair Value	0	0
Insurance contracts in nonqualified trusts, fair value	35	37
Long-term debt, including current installments of long-term debt, fair value	3,227	3,204
Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Equity Securities, FV-NI and without Readily Determinable Fair Value	0	0
Insurance contracts in nonqualified trusts, fair value	0	0
Long-term debt, including current installments of long-term debt, fair value	$ 163	$ 167