Commitments, Contingencies & Guarantees - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended
	Sep. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Loss Contingencies [Line Items]
Incentive awarded to the company by the State of Connecticut, total		$ 11.5
Incentive awarded to the company by the State of Connecticut, non-interest bearing loans	6.0	8.0
Incentive awarded to the company by the State of Connecticut, grants	1.5	3.5
Non-interest bearing incentive loan term		10 years
Incentive awarded to the company by the State of Connecticut, revenue recognized		0.2	0.2
Incentive awarded to the company by the State of Connecticut, deferred revenue	$ 7.5	$ 5.9		$ 6.1