Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Mar. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]
Valuation allowance		$ 56.5
Cumulative operating income loss period considered		3 years
Unrecognized income tax benefits		$ 12.2	$ 11.4
ASU 2016-09 [Member]
Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]
Tax expense on compensation cost	$ 1.5
Change in valuation allowance from offsetting release	(1.5)
Cumulative effect adjustment on accumulated deficit, gross	5.6
Decrease in accumulated deficit due to the recognition of excess tax benefit after valuation allowance	1.8	1.8
Valuation allowance recognized	$ 3.8
Valuation Allowance of Deferred Tax Assets [Member]
Income Loss From Operations Before Provision Benefit For Income Taxes [Line Items]
Valuation allowance related to deferred tax assets from operating loss carryforwards		$ 58.8