Revenue Recognition Accounting Policy (Details 3) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Total Revenues	$ 1,254	$ 1,371
Deferred Revenue	419		$ 414
Deferred Revenue, Revenue Recognized	(17)
Deferred Revenue, Additions	$ 22