Summary of significant accounting policies Revenue (Details) - Over-Reporting of License Revenue - USD ($) $ in Millions	9 Months Ended	96 Months Ended
Dec. 31, 2015	Dec. 31, 2015
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Estimated over recognition of license revenue		$ 1.3
Licenses Revenue
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Reduction in license revenue	$ 1.3

Amount of each individual error being corrected in the correcting adjustment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB TOPIC 1.N.Q3)
-URI http://asc.fasb.org/extlink&oid=26874127&loc=d3e30840-122693

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 1
-Section N

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Balance Type:	debit
Period Type:	duration