Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 99	$ 271
Trading securities	69	61
Total assets	168	332
Contingent Value Right (CVR)	1	2
CVR-related legal liability	260	261
Fair value of interest rate swap agreements	108	76
Total liabilities	369	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	98	155
Trading securities	69	61
Total assets	167	216
Contingent Value Right (CVR)	1	2
Total liabilities	1	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	1	116
Total assets	1	116
Fair value of interest rate swap agreements	108	76
Total liabilities	108	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	260	261
Total liabilities	$ 260	$ 261