Subsequent Events - Additional Information (Detail) In Millions, except Share data, unless otherwise specified	3 Months Ended		0 Months Ended			0 Months Ended		0 Months Ended
	Mar. 31, 2015 ARE-Seattle No. 16, LLC (Landlord) [Member]	Mar. 31, 2015 Fate Therapeutics [Member]	Apr. 06, 2015 Subsequent Event [Member] USD ($)	Apr. 30, 2015 Subsequent Event [Member] sqft	Apr. 30, 2015 Subsequent Event [Member] New Premises [Member] sqft	May 11, 2015 Subsequent Event [Member] Stage Therapeutics GmbH [Member] EUR (€) Employees	May 11, 2015 Subsequent Event [Member] Stage Therapeutics GmbH [Member] Germany [Member] Facilities	May 11, 2015 Subsequent Event [Member] Stage Therapeutics GmbH [Member] Maximum [Member] EUR (€)	Apr. 04, 2015 Subsequent Event [Member] Penn/Novartis Sublicense Agreement [Member] USD ($)	May 11, 2015 Subsequent Event [Member] Fate Therapeutics [Member] USD ($)	May 11, 2015 Subsequent Event [Member] Fate Therapeutics [Member] Maximum [Member]	May 11, 2015 Subsequent Event [Member] Fate Therapeutics [Member] Minimum [Member] USD ($)
Subsequent Event [Line Items]
Upfront license fee									$ 12.25
Percentage of milestone payment reduced									50.00%
Reimbursement of milestone payment									50.00%
Area of leased office and laboratory space				80,000	90,000
Anticipated lease commencement date	Feb. 01, 2017
Initial term of lease	84 months
Base rent per square foot			48.00
Percentage of increase in annual base rent			2.50%
Base rent for first year			4.3
Base rent after rent abatement			2.2
Increased base rent in the final year			5.0
Cash paid for acquisition						52.5
Common stock share issued for acquisition						486,279
Earn out payments in cash contingent upon the achievement of certain milestones								135.0
Number of operating facilities							2
Number of employees						23
Upfront fee paid										5.0
Common stock share purchased										1,000,000
Purchase price of common stock										$ 8.00
Research funding amount per year												2.0
Collaboration and license agreement description		The Company also agreed to provide Fate Therapeutics with research funding of a minimum of $2.0 million per year during the initial four year research term. The Company has an option to extend the collaboration for two additional years, subject to payment of an extension fee and additional annual research funding.
Research funding additional term										2 years
Research funding term											4 years
Fees and milestone payments upon achievement of clinical, regulatory, and commercial milestones										$ 51.5