Locations, Expiration Dates and Square Footage of Principal Leased Properties (Detail)	12 Months Ended
	Dec. 31, 2012 sqft
Cambridge, Massachusetts
Operating Leased Assets [Line Items]
Square footage	1,742
Lease expiration date	2013-06
Bothell, Washington
Operating Leased Assets [Line Items]
Square footage	19,108
Lease expiration date	2013-03
Corvallis, Oregon
Operating Leased Assets [Line Items]
Square footage	53,000
Lease expiration date	2020-12
Corvallis, Oregon land lease
Operating Leased Assets [Line Items]
Lease expiration date	2042-02