Income Taxes -Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Aug. 31, 2004	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Taxes [Line Items]
Amount Equity would be increased		$ 10.0
Change in the valuation allowance		80.1	$ 65.5	$ 66.8
Federal operating loss carryforwards		1,900.0
State operating loss carryforwards		$ 1,300.0
Net operating loss carryforwards	$ 216.0
Net operating loss and credit carryforwards, annual use limitation	$ 13.0
Federal
Income Taxes [Line Items]
Net operating loss carryforwards, expiration year		2018
Research and development credits subject to expiration		$ 49.1
Federal research and development credits begin to expire		2024
State
Income Taxes [Line Items]
Research and development credits not subject to expiration		$ 37.7