Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 309	$ 299
Trading securities	53	80
Total assets	362	379
Contingent Value Right (CVR)	5	1
CVR-related liability	260	252
Fair value of interest rate swap agreements	40	49
Total liabilities	305	302
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	171	163
Trading securities	53	80
Total assets	224	243
Contingent Value Right (CVR)	5	1
Total liabilities	5	1
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	138	136
Total assets	138	136
Fair value of interest rate swap agreements	40	49
Total liabilities	40	49
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 liability	260	252
Total liabilities	$ 260	$ 252