Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 245	$ 65
Trading securities	42	38
Total assets	287	103
Contingent Value Right	16
Fair value of interest rate swap agreements	73	88
Total liabilities	89	88
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	123	65
Trading securities	42	38
Total assets	165	103
Contingent Value Right	16
Total liabilities	16
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	122
Total assets	122
Fair value of interest rate swap agreements	73	88
Total liabilities	$ 73	$ 88