Income Taxes (Narrative) (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015
Operating loss carryforward, expiration date		Dec. 31, 2018
Unrecognized tax benefits	$ 2,100,000	$ 2,100,000	$ 2,100,000
Income tax expense (benefit)	$ (73,000)	(556,000)	$ (73,000)
Income tax expense (benefit) related to reduction of existing deferred tax liability		$ (200,000)
United Kingdom enacted tax rate	20.00%	17.00%	20.00%
Interest and penalties pertaining to income tax examination recognized		$ 0	$ 0
In Process Research and Development [Member]
Income tax expense (benefit) related to reduction of existing deferred tax liability		(400,000)
Impairment of in-process research and development		$ 2,000,000
Maximum [Member]
Income tax examination, years under examination		2015
Minimum [Member]
Income tax examination, years under examination		1998
Domestic Tax Authority [Member]
Net operating loss carryforwards ("NOLs")		$ 190,700,000
Domestic Tax Authority [Member] | Research Tax Credit Carryforward [Member]
Tax credit carryforward		$ 3,100,000
Tax credit carryforward, expiration date		Dec. 31, 2018
Unrecognized tax benefits		$ 2,100,000
Foreign Tax Authority [Member]
Net operating loss carryforwards ("NOLs")		8,900,000
Tax Year 2016 [Member] | Foreign Tax Authority [Member]
Net operating loss carryforwards ("NOLs")		$ 300,000