Summary of Significant Accounting Policies - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018 USD ($)
Notes To Financial Statements [Abstract]
Revenue remaining performance obligation	$ 380.7
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Expected timing	5 years