Annual report pursuant to Section 13 and 15(d)

Revolving Credit Facility (Details)

v2.4.1.9
Revolving Credit Facility (Details) (USD $)
12 Months Ended
Mar. 31, 2015
item
Mar. 31, 2014
Mar. 31, 2013
Jun. 09, 2014
Revolving Credit Facility        
Outstanding borrowings $ 12,953,000us-gaap_LinesOfCreditCurrent $ 13,228,000us-gaap_LinesOfCreditCurrent    
Interest expense 548,000us-gaap_InterestExpense 712,000us-gaap_InterestExpense 717,000us-gaap_InterestExpense  
Amortization of deferred financing costs 196,000us-gaap_AmortizationOfFinancingCosts 223,000us-gaap_AmortizationOfFinancingCosts 148,000us-gaap_AmortizationOfFinancingCosts  
Credit Facility        
Revolving Credit Facility        
Credit and security agreements 2cpst_LineOfCreditFacilityNumberOfCreditAndSecurityAgreements
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
     
Maximum borrowing capacity under facility 15,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
    20,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
Minimum cash balance 11,800,000cpst_DebtInstrumentCovenantComplianceMinimumCashBalance
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
     
Minimum covenant compliance period 12 months      
Variable base rate LIBOR      
Borrowing rate (as a percent) 4.00%us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
4.00%us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
   
Annual unused line fee (as a percent) 0.25%us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
     
Interest rate with respect to letters of credit (as a percent) 1.50%cpst_LettersOfCreditInterestRatePercentage
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
     
Outstanding borrowings 13,000,000us-gaap_LinesOfCreditCurrent
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
13,200,000us-gaap_LinesOfCreditCurrent
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
   
Additional borrowing capacity under facility 1,400,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
     
Interest expense 500,000us-gaap_InterestExpense
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
700,000us-gaap_InterestExpense
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
700,000us-gaap_InterestExpense
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
 
Amortization of deferred financing costs 200,000us-gaap_AmortizationOfFinancingCosts
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
200,000us-gaap_AmortizationOfFinancingCosts
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
100,000us-gaap_AmortizationOfFinancingCosts
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
 
Credit Facility | Forecast        
Revolving Credit Facility        
Restricted cash 5,000,000us-gaap_RestrictedCashAndCashEquivalents
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
/ us-gaap_StatementScenarioAxis
= us-gaap_ScenarioForecastMember
     
Credit Facility | Minimum        
Revolving Credit Facility        
Interest floor amount 66,000cpst_LineOfCreditFacilityInterestFloorAmount
/ us-gaap_CreditFacilityAxis
= us-gaap_LineOfCreditMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
     
Non-revolving capital expense line of credit        
Revolving Credit Facility        
Maximum borrowing capacity under facility       $ 500,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_CreditFacilityAxis
= cpst_NonRevolvingCapitalExpenseLineOfCreditMember