Commitments - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingencies Disclosure [Line Items]
Lease termination notice period	6 months
Rental expense	$ 1.3	$ 0.8	$ 0.9
U.S. Facilities
Commitments and Contingencies Disclosure [Line Items]
Lease expiration date	2017-07
Office and Manufacturing space in United Kingdom
Commitments and Contingencies Disclosure [Line Items]
Lease expiration date	2016-02
Office and Manufacturing Space in Japan
Commitments and Contingencies Disclosure [Line Items]
Lease expiration date	2021-11