Schedule II - Valuation and Qualifying Accounts (Details) (Allowance for Trade Receivables [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Allowance for Trade Receivables [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 3		$ 2		$ 1
Additions Charged to Income	3		2		2
Deductions From Reserves	3	[1]	1	[1]	1	[1]
Balance at End of Period	$ 3		$ 3		$ 2

[1] Deductions from reserves represent losses or expenses for which the respective reserves were created. In the case of the uncollectible accounts reserve, such deductions are net of recoveries of amounts previously written off.