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Commitments - Additional Information (Detail) (USD $)
|
12 Months Ended | ||
|---|---|---|---|
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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| Commitments and Contingencies Disclosure [Abstract] | |||
| Total rent expense | $ 445,000 | $ 457,000 | $ 494,000 |