Amount charged against earnings in the period for incurred and estimated costs associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, excluding asset retirement obligations.

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Carrying amount as of the balance sheet date of known and estimated obligations associated with exit from or disposal of business activities or restructurings pursuant to a duly authorized plan, which are expected to be paid in the next twelve months or in the normal operating cycle if longer. Costs of such activities include those for one-time termination benefits, termination of an operating lease or other contract, consolidating or closing facilities, relocating employees, and costs associated with an ongoing benefit arrangement, but excludes costs associated with the retirement of a long-lived asset.

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Restructuring Charge - Additional Information (Detail) (USD $)	1 Months Ended			6 Months Ended	8 Months Ended
	Apr. 30, 2013 Employee	Jan. 31, 2013 Employee	Nov. 30, 2012 Employee	Jun. 30, 2013 Employee	Jun. 30, 2013	Dec. 31, 2012
Restructuring Cost And Reserve [Line Items]
Number of employees terminated	2	5	16	23
Net restructuring charge				$ 79,000	$ 698,000
Payment of Severance cost				223,000
Accrued restructuring liability				0	0	143,000
Research and Development Expense
Restructuring Cost And Reserve [Line Items]
Net restructuring charge				66,000
General and Administrative Expense
Restructuring Cost And Reserve [Line Items]
Net restructuring charge				$ 13,000