Revenue - Performance Obligations - Tabular Disclosure (Details)	Jun. 30, 2018
Customers, Contracted Revenue, Deferred Revenue
Remaining performance obligations
Remaining performance obligation (as a percent)	100.00%
Customers, Contracted Revenue, Deferred Revenue | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Remaining performance obligations
Remaining performance obligation (as a percent)	77.00%
Remaining performance obligation, expected timing of satisfaction, period	6 months
Customers, Contracted Revenue, Deferred Revenue | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Remaining performance obligations
Remaining performance obligation (as a percent)	15.00%
Remaining performance obligation, expected timing of satisfaction, period	12 months
Customers, Contracted Revenue, Deferred Revenue | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Remaining performance obligations
Remaining performance obligation (as a percent)	8.00%
Remaining performance obligation, expected timing of satisfaction, period
Customers, Contracted Revenue, Backlog
Remaining performance obligations
Remaining performance obligation (as a percent)	100.00%
Customers, Contracted Revenue, Backlog | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Remaining performance obligations
Remaining performance obligation (as a percent)	41.00%
Remaining performance obligation, expected timing of satisfaction, period	6 months
Customers, Contracted Revenue, Backlog | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Remaining performance obligations
Remaining performance obligation (as a percent)	41.00%
Remaining performance obligation, expected timing of satisfaction, period	12 months
Customers, Contracted Revenue, Backlog | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Remaining performance obligations
Remaining performance obligation (as a percent)	18.00%
Remaining performance obligation, expected timing of satisfaction, period