Summary of Restructuring Costs by Function (Parenthetical) (Detail) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Restructuring And Related Activities [Abstract]
Accelerated depreciation	$ 0.8
Acceleration of stock option vesting	$ 0.1

Amount of accelerated depreciation charged against earnings associated with exit from or disposal of business activities or restructuring plan.

No definition available.

Name:	us-gaap_RestructuringReserveAcceleratedDepreciation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration