Business Acquisitions - Reconciliation of Consideration Transferred to Total Cash Paid to Acquire Business (Detail) - Crescendo Biosciences, Inc. $ in Millions	Feb. 28, 2014 USD ($)
Schedule of Business Acquisitions, Cost of Acquired Entity [Line Items]
Total consideration transferred	$ 259.0
Share-based compensation to Crescendo employees	6.9
Change of control payments to Crescendo employees	5.7
Offset: Non-cash fair value purchase option	(8.0)
Total cash paid	$ 263.6