Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax [Line Items]
State income tax provision	$ 1,300,000	$ 330,000	$ 0
Federal R&D credit carryforwards	15,100,000
Net operating loss carryforwards related to excess tax deductions for stock compensation	99,300,000
Increase in valuation allowance of deferred tax assets	26,200,000
Unrecognized tax reserves recorded during period	363,000	2,301,000	0
Total unrecognized tax benefits that would reduce the annual effective tax rate if recognized	0
Interest and/or penalties accrued	0	0
Interest and/or penalties	0	$ 0	$ 0
Federal
Income Tax [Line Items]
Operating loss carryforwards	$ 438,500,000
Remaining net operating loss carryforward, expiration year	2019
Federal | Expiring in 2018
Income Tax [Line Items]
Operating loss carryforwards	$ 2,300,000
State
Income Tax [Line Items]
Operating loss carryforwards	$ 380,800,000
Remaining net operating loss carryforward, expiration year	2018
Net operating loss carryforwards with no expiration date	$ 9,000,000
State | Expiring in 2017
Income Tax [Line Items]
Operating loss carryforwards	39,400,000
Foreign
Income Tax [Line Items]
Operating loss carryforwards	427,000,000
Net operating loss carryforwards with no expiration date	3,100,000
Foreign | Operating Loss Carryforwards Expiring 2022
Income Tax [Line Items]
Operating loss carryforwards	423,900,000
Expire in 2018
Income Tax [Line Items]
Federal R&D credit carryforwards	$ 119,000