Commitments and Contingencies - Narrative (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended	12 Months Ended
	Jun. 26, 2015	Oct. 31, 2015	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Jul. 21, 2014	Dec. 31, 2013
Loss Contingencies [Line Items]
Rent expense				$ 0.5	$ 0.6
CARB
Loss Contingencies [Line Items]
Calculated penalty for alleged violations	$ 1.8
Settlement, amount awarded to other party			$ 0.1
Applied Utility Systems Inc | Sales And Use Tax Audit
Loss Contingencies [Line Items]
Sales tax owed							$ 1.5
Reduction income tax, original						$ 12.2
Reduction income tax						$ 9.0
Settlement of case amount		$ 0.1
Applied Utility Systems Inc | Sales And Use Tax Audit | Maximum
Loss Contingencies [Line Items]
Sales tax owed				$ 0.9