Income Taxes - Deferred Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Increase in valuation allowance	$ 14,186	$ 21,463	$ 32,692
Federal and state NOL carryforwards	250,200	238,800
Research and development tax credit carryforwards	$ 12,900	$ 10,300