Revenue Recognition - Remaining Performance Obligations, Expected Timing of Satisfaction (Details)	Jun. 30, 2019	Dec. 31, 2018
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Remaining Performance Obligations
Percentage of remaining performance obligation expected to be recognized		60.00%
Duration of expected recognition period for remaining performance obligation		2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Remaining Performance Obligations
Percentage of remaining performance obligation expected to be recognized	60.00%
Duration of expected recognition period for remaining performance obligation	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Remaining Performance Obligations
Percentage of remaining performance obligation expected to be recognized		35.00%
Duration of expected recognition period for remaining performance obligation		3 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-07-01
Remaining Performance Obligations
Percentage of remaining performance obligation expected to be recognized	35.00%
Duration of expected recognition period for remaining performance obligation	3 years