Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 268	$ 271
Trading securities	63	61
Total assets	331	332
Contingent Value Right (CVR)	2	2
CVR-related legal liability	261	261
Fair value of interest rate swap agreements	105	76
Total liabilities	368	339
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	154	155
Trading securities	63	61
Total assets	217	216
Contingent Value Right (CVR)	2	2
Total liabilities	2	2
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	114	116
Total assets	114	116
Fair value of interest rate swap agreements	105	76
Total liabilities	105	76
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
CVR-related legal liability	261	261
Total liabilities	$ 261	$ 261