Summary of Significant Accounting Policies - Research and Development (Details)	12 Months Ended
Mar. 31, 2020 USD ($)
Research and Development ("R&D")
Total offsets to R&D expenses	$ 0

Represents the amount of grant distributions and development funding that has been offset to research and development expenses.

No definition available.

Name:	cpst_ResearchAndDevelopmentOffsetToExpenses
Namespace Prefix:	cpst_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration