Fair Value Measurements (Details) - USD ($) $ in Thousands | Sep. 30, 2016 | Dec. 31, 2015 |
U.S. government agency notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | | $ 0 |
Recurring basis | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total financial assets | $ 60,307 | 70,195 |
Financial liabilities measured at fair value | 0 | 0 |
Recurring basis | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total financial assets | 28,671 | 8,169 |
Recurring basis | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total financial assets | 31,636 | 62,026 |
Recurring basis | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total financial assets | 0 | 0 |
Recurring basis | U.S. treasury bills | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 1,999 | |
Short-term investments: | 9,491 | 41,282 |
Long-term investments: | | 4,590 |
Recurring basis | U.S. treasury bills | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 1,999 | |
Short-term investments: | 9,491 | 0 |
Long-term investments: | | 0 |
Recurring basis | U.S. treasury bills | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 0 | 41,282 |
Long-term investments: | | 4,590 |
Recurring basis | U.S. treasury bills | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 0 | 0 |
Long-term investments: | | 0 |
Recurring basis | U.S. government agency notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 600 | 4,385 |
Short-term investments: | 9,643 | 11,769 |
Recurring basis | U.S. government agency notes | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 0 | 0 |
Short-term investments: | 0 | 0 |
Recurring basis | U.S. government agency notes | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 600 | 4,385 |
Short-term investments: | 9,643 | 11,769 |
Recurring basis | U.S. government agency notes | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 0 | |
Short-term investments: | 0 | 0 |
Recurring basis | Commercial paper | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 6,399 | |
Short-term investments: | 2,691 | |
Recurring basis | Commercial paper | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 0 | |
Short-term investments: | 0 | |
Recurring basis | Commercial paper | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 6,399 | |
Short-term investments: | 2,691 | |
Recurring basis | Commercial paper | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 0 | |
Short-term investments: | 0 | |
Recurring basis | U.S. treasury bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 15,045 | |
Recurring basis | U.S. treasury bonds | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 15,045 | |
Recurring basis | U.S. treasury bonds | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 0 | |
Recurring basis | U.S. treasury bonds | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 0 | |
Recurring basis | Corporate notes | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 10,298 | |
Long-term investments: | 2,005 | |
Recurring basis | Corporate notes | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 0 | |
Long-term investments: | 0 | |
Recurring basis | Corporate notes | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 10,298 | |
Long-term investments: | 2,005 | |
Recurring basis | Corporate notes | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Short-term investments: | 0 | |
Long-term investments: | 0 | |
Recurring basis | Money market funds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 2,136 | 8,169 |
Recurring basis | Money market funds | Quoted Prices in Active Markets (Level 1) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 2,136 | 8,169 |
Recurring basis | Money market funds | Significant Other Observable Inputs (Level 2) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | 0 | 0 |
Recurring basis | Money market funds | Unobservable Inputs (Level 3) | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Cash equivalents: | $ 0 | $ 0 |