Rendering

Component: (Network and Table)
Network
153 - Disclosure - Effective Income Tax Rate (Detail)
(http://www.alnylam.com/taxonomy/role/DisclosureEffectiveIncomeTaxRate)
TableReconciliation of Provision of Income Taxes [Table]
Slicers (applies to each fact value in each table cell)
Reconciliation of Provision of Income Taxes [Line Items]Period [Axis]
2012-01-01 - 2012-12-31
2011-01-01 - 2011-12-31
2010-01-01 - 2010-12-31
At U.S. federal statutory rate
.350  
.350  
.350  
State taxes, net of federal effect
.049  
.046  
.042  
Stock compensation
(.007) 
(.033) 
(.050) 
Other permanent items
(.016) 
(.002) 
.013  
Valuation allowance
(.285) 
(.361) 
(.367) 
Effective income tax rate
.091  
 
 
 
(.012)