Fair Value Measurements and Derivatives - Fair Value of Financial Instruments (Details) - USD ($) $ in Millions	Jun. 30, 2017		Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Carrying Value	$ 1,871		$ 1,670
Fair Value	1,945		1,713
Other indebtedness [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Carrying Value	21		120
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Market Approach Valuation Technique [Member] | Senior Notes Total [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Carrying Value	1,850		1,550
Fair Value	1,931		1,612
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Income Approach Valuation Technique [Member] | Other indebtedness [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Carrying Value	21	[1]	120
Fair Value	$ 14		$ 101

[1] *The carrying value includes the unamortized portion of a fair value adjustment related to a terminated interest rate swap at both dates. The carrying value and fair value also include a financial liability associated with certain build-to-suit lease arrangements at both dates.