Fair Value Measurements (Schedule of Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost investments, carrying amount	$ 155	$ 151
Cost investments, fair value	0	0
Insurance contracts in nonqualified pension trusts, carrying amount	49	55
Insurance contracts in nonqualified pension trusts, fair value	49	55
Long-term debt, including current installments of long-term debt, carrying amount	2,938	2,542
Long-term debt, including current installments of long-term debt, fair value	3,043	2,586
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 pension trusts, fair value	49	55
Long-term debt, including current installments of long-term debt, fair value	2,826	2,348
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 pension trusts, fair value	0	0
Long-term debt, including current installments of long-term debt, fair value	$ 217	$ 238