Annual report pursuant to Section 13 and 15(d)

Federal Income Tax Provision Compared With Statutory Rates (Detail)

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Federal Income Tax Provision Compared With Statutory Rates (Detail)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Income Tax Disclosure [Abstract]      
Statutory regular federal income tax rate (34.00%) (34.00%) (34.00%)
Change in valuation allowance 40.20% 37.40% 27.00%
Tax return to prior year provision adjustments     (0.90%)
Reduction of net operating loss attributes     (3.10%)
State tax benefit (net of federal benefit) (3.10%) (3.30%) (4.20%)
Research credits (3.10%) (1.90%) (2.10%)
Foreign amounts with no tax benefit 0.10% (0.10%) (0.20%)
Non-deductible expenses 0.40% 1.00% 1.60%
Effect of change in rate 0.90% 2.30% 14.20%
Other (0.50%) (0.80%) 0.30%
Total 0.90% 0.60% (1.40%)