Revenue - Remaining Performance Obligations (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2018 USD ($)
Revenue from Contract with Customer [Abstract]
Remaining performance obligations	$ 154,497
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing	1 year
Remaining performance obligations, percentage	80.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-07-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing	2 years
Remaining performance obligations, percentage	20.00%