Pension and Retirement Plans (Detail)	6 Months Ended	12 Months Ended
Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2015
Compensation and Retirement Disclosure [Abstract]
Number of years defined benefit plans are closed to newly hired employees	2 years	2 years	2 years

Number of years that all of the Company's defined benefit plans are closed to newly hired employees.

No definition available.

Name:	cspi_NumberOfYearsDefinedBenefitPlansAreClosedToNewlyHiredEmployees
Namespace Prefix:	cspi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration