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Fair Value Measurements and Marketable Securities - Financial Assets at Fair Value on Recurring Basis (Detail) (USD $)
In Thousands, unless otherwise specified
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Mar. 31, 2015
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Dec. 31, 2014
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
$ 82,037 |
$ 58,577 |
| Basis of Fair Value Measurements, Level 1 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
10,366 |
3,369 |
| Basis of Fair Value Measurements, Level 2 |
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|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
71,671 |
55,208 |
| Basis of Fair Value Measurements, Level 3 |
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|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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| Total cash equivalents and marketable securities |
0 |
0 |
| Money Market Funds |
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|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
10,366 |
3,369 |
| Money Market Funds | Basis of Fair Value Measurements, Level 1 |
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|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
10,366 |
3,369 |
| Money Market Funds | Basis of Fair Value Measurements, Level 3 |
|
|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
0 |
0 |
| Certificates of Deposit |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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|
| Total cash equivalents and marketable securities |
1,475 |
2,505 |
| Certificates of Deposit | Basis of Fair Value Measurements, Level 2 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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|
| Total cash equivalents and marketable securities |
1,475 |
2,505 |
| Certificates of Deposit | Basis of Fair Value Measurements, Level 3 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
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| Total cash equivalents and marketable securities |
0 |
0 |
| Corporate Debt Securities |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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|
| Total cash equivalents and marketable securities |
31,935 |
28,081 |
| Corporate Debt Securities | Basis of Fair Value Measurements, Level 2 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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|
| Total cash equivalents and marketable securities |
31,935 |
28,081 |
| Corporate Debt Securities | Basis of Fair Value Measurements, Level 3 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
0 |
0 |
| Government Securities |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
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| Total cash equivalents and marketable securities |
24,021 |
19,123 |
| Government Securities | Basis of Fair Value Measurements, Level 2 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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| Total cash equivalents and marketable securities |
24,021 |
19,123 |
| Government Securities | Basis of Fair Value Measurements, Level 3 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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|
| Total cash equivalents and marketable securities |
0 |
0 |
| Commercial Paper |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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|
| Total cash equivalents and marketable securities |
14,240 |
5,499 |
| Commercial Paper | Basis of Fair Value Measurements, Level 2 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
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| Total cash equivalents and marketable securities |
14,240 |
5,499 |
| Commercial Paper | Basis of Fair Value Measurements, Level 3 |
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| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |
|
|
| Total cash equivalents and marketable securities |
$ 0 |
$ 0 |