Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2013	Dec. 31, 2010
Commitments and Contingencies Disclosure [Line Items]
Minimum term of non-cancellable operating leases	1 year
Expiration of non-cancellable operating leases maximum year	2019
Financing for leasehold improvement		$ 1.1
Outstanding liability related to leasehold improvements	0.8
Leasehold Improvements reflected in Accrued liabilities	0.1
Leasehold Improvements reflected in Other non-current liabilities	$ 0.7
Concord Lease
Commitments and Contingencies Disclosure [Line Items]
Early termination of non-cancellable operating leases minimum period	2015-01

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Earliest period for early termination of non-cancelable operating lease.

No definition available.

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Latest period of expiration of non-cancelable operating lease.

No definition available.

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Portion of outstanding liability related to leasehold improvement reflected in accrued liabilities.

No definition available.

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Portion of outstanding liability related to leasehold improvement reflected in other non current liabilities.

No definition available.

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Minimum term of non-cancelable operating lease.

No definition available.

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Outstanding liability related to leasehold improvements current and non current.

No definition available.

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Proceeds from landlord for financing leasehold improvement.

No definition available.

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