Commitments and Contingencies - Summary of Liability Related to Lease (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012
Commitments And Contingencies Disclosure [Abstract]
Balance as of January 1	$ 1,103	$ 452
Net rental receipts (payments)	(111)	(19)
Accretion of discount	41	18
Increase in net estimated contract termination costs	79	39
Balance as of June 30	$ 1,112	$ 490

Amount recognized for the passage of time, typically for liabilities, that have been discounted to their net present values. Excludes accretion associated with asset retirement obligations.

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Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

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Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

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