Debt Estimated Fair Value of Significant Financial Instruments (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Carrying Amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	$ 432	$ 334
Long-term debt	2,619	2,621
Fair Value [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term debt	439	334
Long-term debt	$ 2,844	$ 2,819