Fair Value Measurements (Schedule of Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost investments, carrying amount	$ 158	$ 155
Cost investments, fair value	0	0
Insurance contracts in nonqualified trusts, carrying amount	49	49
Insurance contracts in nonqualified trusts, fair value	49	49
Long-term debt, including current installments of long-term debt, carrying amount	2,905	2,938
Long-term debt, including current installments of long-term debt, fair value	3,011	3,043
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost investments, fair value	0	0
Insurance contracts in nonqualified trusts, fair value	49	49
Long-term debt, including current installments of long-term debt, fair value	2,796	2,826
Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost investments, 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	$ 215	$ 217