Fair Value Measurements (Schedule of Carrying Values and Fair Values of Financial Instruments) (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost investments, carrying amount	$ 151	$ 145
Cost investments, fair value	0	0
Insurance contracts in nonqualified pension trusts, carrying amount	55	56
Insurance contracts in nonqualified pension trusts, fair value	55	56
Long-term debt, including current installments of long-term debt, carrying amount	2,542	2,633
Long-term debt, including current installments of long-term debt, fair value	2,586	2,658
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	55	56
Long-term debt, including current installments of long-term debt, fair value	2,348	2,398
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	$ 238	$ 260