Fair Value Measurements (Schedule of Carrying Values and Fair Values of Financial Instruments) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cost investments, carrying amount	$ 147	$ 156
Cost investments, fair value	0	0
Insurance contracts in nonqualified trusts, carrying amount	62	66
Insurance contracts in nonqualified trusts, fair value	62	66
Long-term debt, including current installments of long-term debt, carrying amount	2,893	2,990
Long-term debt, including current installments of long-term debt, fair value	2,954	3,130
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	62	66
Long-term debt, including current installments of long-term debt, fair value	2,706	2,886
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	$ 248	$ 244