Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity (Details 5)

Stockholders' Equity (Details 5) (USD $)	0 Months Ended			1 Months Ended	12 Months Ended			0 Months Ended
Stockholders' Equity (Details 5) (USD $)	May 06, 2014	Sep. 18, 2012	Mar. 05, 2012 item	Mar. 31, 2012	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2013	Oct. 31, 2013
Stockholders' Equity
Options outstanding (in shares)					13,200,000	12,900,000	11,800,000
Restricted stock units outstanding (in shares)					1,900,000	2,100,000	1,500,000
Common stock sold (in shares)	18,800,000		22,600,000
Number of preferred stock purchase right for each share of common stock					1
Preferred stock, par value (in dollars per share)					$ 0.001	$ 0.001
Purchase price (in dollars per share)					$ 10.00
Period following public announcement of beneficial ownership acquired by various persons resulting in rights becoming exercisable					10 days
Beneficial ownership of common stock (as a percent)					20.00%
Period following commencement of tender offer or exchange offer that would result in acquisition of beneficial ownership various persons resulting in rights becoming exercisable					10 days
Share Price	$ 1.70us-gaap_SharePrice
Net proceeds from sale of the common stock, after deducting fees and other offering expenses (in dollars)	$ 29,800,000
Common stock, par value (in dollars per share)			$ 0.001		$ 0.001	$ 0.001
Unsolicited exercise of 2012 warrants			22,600,000
Exercise price (in dollars per share)		$ 1.26	$ 1.55				$ 1.41
Warrant unit price (in dollars per shares)			$ 1.11
Number of shares of common stock in each unit			1
Number of shares of common stock in each warrant			1
Right to purchase maximum additional number of shares of common stock under put option			19,000,000
Number of Put Options			2cpst_NumberOfPutOptions
Number of trading days prior to the exercise of put option				30 days
Proceeds from exercise of common stock warrants and put options					29,772,000us-gaap_ProceedsFromIssuanceOfWarrants	5,954,000us-gaap_ProceedsFromIssuanceOfWarrants	4,250,000us-gaap_ProceedsFromIssuanceOfWarrants
Number of investors with whom Investor Agreement entered		1
Purchase price of additional shares determined pursuant to the Investor Agreement (in dollars per share)		$ 0.94
Proceeds from unsolicited exercise of 2012 warrants		4,200,000us-gaap_ProceedsFromWarrantExercises
Outstanding warrants (in shares)							22,600,000
Non-qualified stock options
Stockholders' Equity
Options outstanding (in shares)					3,800,000
Minimum
Stockholders' Equity
Arithmetic average of the average daily trading volumes on the exercise date (in shares)		1,750,000
Stock options
Stockholders' Equity
Options outstanding (in shares)					13,163,363	12,851,688
Options granted (in shares)					1,085,800
Stock options \| Non-qualified stock options
Stockholders' Equity
Options outstanding (in shares)					3,800,000
Options granted (in shares)					250,000
Stock options \| Executive Vice President and Chief Executive Officer \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					2,000,000
Stock options \| Executive vice president of sales and marketing \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					850,000
Stock options \| Former Senior vice president of customer service \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					250,000
Stock options \| Former Senior Vice President of Program Management \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					250,000
Stock options \| Former Senior vice president of human resources \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					200,000
Stock options \| Vice President of Operations \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					250,000
Non-qualified stock options issued prior to Fiscal 2013
Stockholders' Equity
Options granted (in shares)					31,250
Non-qualified stock options issued prior to Fiscal 2013 \| Non-qualified stock options
Stockholders' Equity
Options granted (in shares)					3,300,000
Non-qualified stock options issued prior to Fiscal 2015
Stockholders' Equity
Options granted (in shares)					62,500
Restricted stock units
Stockholders' Equity
Options outstanding (in shares)					93,750
Restricted stock units outstanding (in shares)					93,750
Restricted stock units \| Former Senior vice president of customer service
Stockholders' Equity
Options granted (in shares)					31,250
Restricted stock units \| Vice President of Operations
Stockholders' Equity
Options granted (in shares)					62,500
March 2012
Stockholders' Equity
Proceeds from exercise of common stock warrants and put options				23,100,000
Expenses incurred upon the exercise of warrants				1,900,000
Number of warrants exercised (in shares)					4,725,000			4,700,000
Proceeds from unsolicited exercise of 2012 warrants								$ 6,000,000
Outstanding warrants (in shares)				22,550,000			22,550,000
September 2008
Stockholders' Equity
Outstanding warrants (in shares)				3,910,034			3,961,471
Series A Junior Participating Preferred Stock
Stockholders' Equity
Preferred stock conversion basis					0.01