Debt (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$ 799	$ 799
5.9% Senior Notes, due 2017
Debt Instrument [Line Items]
Long-term debt	400	400
Interest rate	5.90%	5.90%
Unamortized debt discount on senior notes (less than $1 million for 5.9% Senior Notes)	1
6.55% Senior Notes, due 2037
Debt Instrument [Line Items]
Long-term debt	399	399
Interest rate	6.55%	6.55%
Unamortized debt discount on senior notes (less than $1 million for 5.9% Senior Notes)	$ 1