Revenue Recognition - Performance Obligations (Details) $ in Millions	Sep. 30, 2019 USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligation amount	$ 467
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation amount	$ 119
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of remaining performance obligation, period	3 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation amount	$ 111
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Remaining performance obligation amount	$ 237
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing of remaining performance obligation, period