Revenue Recognition Remaining Performance Obligations (Details) $ in Millions	Mar. 31, 2019 USD ($)
Revenue Recognition and Deferred Revenue [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 750
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue Recognition and Deferred Revenue [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 194
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue Recognition and Deferred Revenue [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 203
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue Recognition and Deferred Revenue [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 152
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year