Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities	$ 137
Available-for-sale securities	93	$ 252
Trading securities	11	37
Fair value of interest rate swap agreements	3	1
Total assets	244	290
Contingent Value Right (CVR)		2
CVR-related liability		256
Fair value of interest rate swap agreements	2	18
Total liabilities	2	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]
Investments in equity securities	137
Available-for-sale securities		132
Trading securities		37
Total assets	137	169
Contingent Value Right (CVR)		2
Total liabilities		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	93	120
Trading securities	11
Fair value of interest rate swap agreements	3	1
Total assets	107	121
Fair value of interest rate swap agreements	2	18
Total liabilities	$ 2	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		256
Total liabilities		$ 256