Collaborative Agreements (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended		3 Months Ended	134 Months Ended	3 Months Ended	0 Months Ended	1 Months Ended	0 Months Ended	1 Months Ended		0 Months Ended		1 Months Ended		3 Months Ended					0 Months Ended		0 Months Ended
	Mar. 31, 2012	Mar. 31, 2010	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2013 GSK item	Oct. 28, 2010 GSK Original Collaboration Agreement	Oct. 31, 2010 GSK Original Collaboration Agreement	Jul. 17, 2012 GSK Expanded Collaboration Agreement item	Jul. 31, 2012 GSK Expanded Collaboration Agreement	Mar. 31, 2013 GSK Expanded Collaboration Agreement	Jul. 26, 2012 GSK SPA	Jul. 17, 2012 GSK SPA	Jul. 31, 2012 GSK SPA	Mar. 31, 2013 GSK SPA	Jun. 30, 2012 GSK Clinical development objectives and the acceptance of regulatory filings milestone	Jun. 30, 2012 GSK Clinical development objectives and the acceptance of regulatory filings milestone Original Collaboration Agreement	Oct. 28, 2010 GSK Clinical development objectives and the acceptance of regulatory filings milestone Original Collaboration Agreement	Oct. 28, 2010 GSK Market approvals for migalastat HCl milestone Original Collaboration Agreement	Oct. 28, 2010 GSK Achievement of certain sales thresholds milestone Original Collaboration Agreement	Jul. 17, 2012 GSK U.S. regulatory approval milestones for migalastat HCl monotherapy and migalastat HCl-ERT co-administration	Jul. 17, 2012 GSK U.S. regulatory approval milestones for migalastat HCl monotherapy and migalastat HCl-ERT co-administration Expanded Collaboration Agreement	Jul. 17, 2012 GSK U.S. regulatory approval milestones for migalastat HCl monotherapy and migalastat HCl-ERT co-administration Expanded Collaboration Agreement Maximum
Collaborative Agreements
Upfront payment received						$ 30,000,000
Potential milestone payments receivable						173,500,000										3,500,000	13,500,000	80,000,000	80,000,000		20,000,000
Percentage of development costs funded by the entity								40.00%
Stock issued from collaboration agreement (in shares)		4.90				6.90	6.87					2.90	2.90
Price per share of common stock issued as part of the license and collaboration agreement (in dollars per share)	$ 5.70	$ 3.74	$ 5.70			$ 4.56	$ 4.56					$ 6.30	$ 6.30
Percentage of premium on average price per share of common stock issued as part of the license and collaboration agreement						30.00%
Period preceding the closing date of the transaction over which average price per share of the company's stock is used						60 days
Total value of the equity investment to the company	62,000,000	17,100,000	62,063,000	193,441,000		31,000,000	31,000,000		18,600,000
Ownership position in the company (as a percent)										19.80%				19.80%
Number of accounting units					1
Milestone revenue recognized															3,500,000
Number of exclusive licenses								2
Additional potential milestone payments receivable																						35,000,000
Period of additional potential milestone payments receivable																						7 years
Percentage of development costs funded by the entity in 2012																				25.00%
Percentage of development costs funded by the counterparty in 2012																				75.00%
Percentage of development costs funded by the entity, thereafter																				40.00%
Percentage of development costs funded by the counterparty, thereafter																				60.00%
Percentage of development costs funded by the counterparty								60.00%
Total purchase price (in dollars)											$ 18,600,000	$ 18,600,000
Lock-up period for common stock issued as a part of SPA											6 months