Restructuring Actions - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Dec. 31, 2013 Position	Sep. 30, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring expenses	$ 4.8
Number of positions reduced	155
Employee separation costs
Research and development expense
Restructuring Cost and Reserve [Line Items]
Employee separation costs	2.2
Selling, general and administrative expense
Restructuring Cost and Reserve [Line Items]
Employee separation costs	$ 2.6