Fair Value Measurements (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Trading securities	$ 9	$ 22
Available-for-sale securities	139	133
Interest rate swap agreements	61	53
Other [assets]	29	17
Fair Value, Assets Measured on Recurring Basis, Total	238	225
Other [liabilities]	235	91
Fair Value Liabilities Measured On Recurring Basis, Total	235	$ 91
Fair Value, Inputs, Level 1 [Member]
Trading securities	9
Available-for-sale securities	0
Interest rate swap agreements	0
Other [assets]	0
Fair Value, Assets Measured on Recurring Basis, Total	9
Other [liabilities]	0
Fair Value Liabilities Measured On Recurring Basis, Total	0
Fair Value, Inputs, Level 2 [Member]
Trading securities	0
Available-for-sale securities	125
Interest rate swap agreements	61
Other [assets]	10
Fair Value, Assets Measured on Recurring Basis, Total	196
Other [liabilities]	235
Fair Value Liabilities Measured On Recurring Basis, Total	235
Fair Value, Inputs, Level 3 [Member]
Trading securities	0
Available-for-sale securities	14
Interest rate swap agreements	0
Other [assets]	19
Fair Value, Assets Measured on Recurring Basis, Total	33
Other [liabilities]	0
Fair Value Liabilities Measured On Recurring Basis, Total	$ 0