Commitments and Contingencies - California Air Resources Board ("CARB") (Details) - CARB - USD ($) $ in Millions		1 Months Ended		6 Months Ended
	Jun. 26, 2015	Jul. 31, 2016	Apr. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Loss contingency, estimate
Calculated penalty for alleged violations	$ 1.8	$ 0.1	$ 0.2	$ 0.8
Amount accrued				$ 0.1
Maximum
Loss contingency, estimate
Amount accrued					$ 0.1
Proposed settlement			$ 0.1