Accounts Receivable (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Accounts Receivable [Abstract]
Bad debt expense	$ 12	$ 12	$ 25	$ 25