Income Taxes - Net Operating Loss and Tax Credit Carryforwards (Details) $ in Millions	Mar. 31, 2020 USD ($)
Income Taxes
Annual limitation amount on utilization of the NOLs and tax credits	$ 57.3

Represents the amount of annual limitation on the utilization of net operating losses and tax credits.

No definition available.

Name:	cpst_AnnualLimitationAmountOnNetOperatingLossesAndTaxCreditsUtilization
Namespace Prefix:	cpst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant