Fair Value (Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis) (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments in equity securities	$ 131	$ 137
Available-for-sale securities	95	93
Trading securities	11	11
Fair value of interest rate swap agreements		3
Total assets	237	244
Fair value of interest rate swap agreements	2	2
Total liabilities	2	2
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	131	137
Total assets	131	137
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	95	93
Trading securities	11	11
Fair value of interest rate swap agreements		3
Total assets	106	107
Fair value of interest rate swap agreements	2	2
Total liabilities	$ 2	$ 2