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Fair Value Measurements and Marketable Securities - Summary of Company's Available-for-Sale Securities (Detail) (USD $)
In Thousands, unless otherwise specified |
Dec. 31, 2012
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Dec. 31, 2011
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|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | $ 59,808 | $ 14,409 |
| Unrealized Gain | 18 | 2 |
| Unrealized Loss | (7) | (3) |
| Fair Value | 59,819 | 14,408 |
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Money market funds [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 5,886 | 4,050 |
| Fair Value | 5,886 | 4,050 |
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Certificate of deposits [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 1,185 | |
| Fair Value | 1,185 | |
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Corporate debt securities [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 20,237 | 4,693 |
| Unrealized Gain | 6 | |
| Unrealized Loss | (1) | (3) |
| Fair Value | 20,242 | 4,690 |
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Government securities [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 27,893 | 5,968 |
| Unrealized Gain | 12 | 2 |
| Unrealized Loss | (6) | |
| Fair Value | 27,899 | 5,970 |
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Commercial paper [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 15,613 | 5,548 |
| Fair Value | 15,613 | 5,548 |
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Marketable Securities Including Cash Equivalents [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | 70,814 | 20,259 |
| Unrealized Gain | 18 | 2 |
| Unrealized Loss | (7) | (3) |
| Fair Value | 70,825 | 20,258 |
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Less cash equivalents [Member]
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Cost Basis | (11,006) | (5,850) |
| Fair Value | $ (11,006) | $ (5,850) |