Valuation And Qualifying Accounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Valuation and Qualifying Accounts [Abstract]
Beginning balance, January 1	$ 3	$ 2	$ 2
Additions charged to costs and expenses	3	2	1
Deductions	(2)	(1)	(1)
Ending balance, December 31	$ 4	$ 3	$ 2