Summary of Warrant Activity (Detail) - Warrants	6 Months Ended
	Jun. 30, 2016 $ / shares shares
Shares
Beginning Balance | shares	10,094,000
Forfeited or cancelled | shares	(723,000)
Ending Balance | shares	9,371,000
Warrants exercisable at June 30, 2016 | shares	9,236,000
Vested warrants expired during the quarter ended June 30, 2016 | shares	(723,000)
Weighted Average Grant Date Fair Value
Beginning Balance | $ / shares	$ 4.18
Weighted Average Exercise Price, Forfeited, cancelled, or expired | $ / shares	6.50
Ending Balance | $ / shares	4.00
Warrants exercisable at June 30, 2016 | $ / shares	4.00
Vested warrants expired during the quarter ended June 30, 2016 | $ / shares	$ 6.50