Revenue Recognition Remaing Performance Obligation (Details) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01 $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation	$ 692
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	12 months