Summary of Significant Accounting Policies - Research and Development (Details) - USD ($) $ in Millions	12 Months Ended
Mar. 31, 2022	Mar. 31, 2021
Research and Development ("R&D")
Total offsets to R&D expenses	$ 0.0	$ 0.0

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

No definition available.

Name:	cgrn_ResearchAndDevelopmentOffsetToExpenses
Namespace Prefix:	cgrn_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration