Business combinations - Estimated Fair Value of Assets Acquired and Liabilities Assumed (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Jun. 30, 2014
Business Acquisition [Line Items]
Gene editing platform intangible asset		$ 30,100
Goodwill	13,128
Pregenen [Member]
Business Acquisition [Line Items]
Cash		420
Gene editing platform intangible asset		30,100
Goodwill		13,128
Other assets acquired		111
Total assets acquired		43,759
Deferred tax liabilities		11,797
Other liabilities assumed		971
Total liabilities assumed		12,768
Net assets acquired		$ 30,991