Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale securities	$ 119	$ 252
Investments in equity securities	149
Trading securities		37
Fair value of interest rate swap agreements	10	1
Total assets	278	290
Contingent Value Right (CVR)	3	2
CVR-related liability	259	256
Fair value of interest rate swap agreements	4	18
Total liabilities	266	276
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		132
Investments in equity securities	149
Trading securities		37
Total assets	149	169
Contingent Value Right (CVR)	3	2
Total liabilities	3	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	119	120
Fair value of interest rate swap agreements	10	1
Total assets	129	121
Fair value of interest rate swap agreements	4	18
Total liabilities	4	18
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	259	256
Total liabilities	$ 259	$ 256