Subsequent Event - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		6 Months Ended
	Jul. 25, 2018	Jun. 30, 2018
Subsequent Event [Line Items]
Restricted stock to be granted, average price per share		$ 44.30
Merger Agreement [Member] | Prevoty, Inc [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Outstanding unvested shares aggregate exchange price to be paid	$ 0.6
Cash deposited into escrow fund as security for indemnification obligations	$ 21.0
Escrow fund period	18 months
Merger Agreement [Member] | Prevoty, Inc [Member] | Subsequent Event [Member] | 2015 Equity Inducement Plan [Member]
Subsequent Event [Line Items]
Restricted stock to be granted, estimated value	$ 4.6
Restricted stock to be granted, average price per share	$ 56.35
Pahlmeyer Acquisition Sub, Inc. [Member] | Merger Agreement [Member] | Prevoty, Inc [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Payments for plan of merger	$ 140.0