Investments and Fair Value Disclosures - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) | Sep. 30, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | $54,027 | [1] | $48,837 | [1] |
Total investments | 123,735 | | 117,004 | |
Total assets, Fair value | 177,762 | | 165,841 | |
Recurring | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 54,027 | [1] | 48,837 | [1] |
Total investments | 123,735 | | 117,004 | |
Total assets, Fair value | 177,762 | | 165,841 | |
Recurring | Money market funds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 54,008 | | 48,256 | |
Recurring | Certificates of deposit | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 19 | | 581 | |
Recurring | U.S. agency notes | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 54,261 | | 50,540 | |
Recurring | Commercial paper | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 7,997 | | 4,999 | |
Recurring | Corporate bonds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 61,477 | | 61,465 | |
Level 1 | Recurring | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 54,027 | [1] | 48,837 | [1] |
Total investments | 0 | | 0 | |
Total assets, Fair value | 54,027 | | 48,837 | |
Level 1 | Recurring | Money market funds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 54,008 | | 48,256 | |
Level 1 | Recurring | Certificates of deposit | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 19 | | 581 | |
Level 1 | Recurring | U.S. agency notes | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 0 | | 0 | |
Level 1 | Recurring | Commercial paper | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 0 | | 0 | |
Level 1 | Recurring | Corporate bonds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 0 | | 0 | |
Level 2 | Recurring | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 0 | [1] | 0 | [1] |
Total investments | 123,735 | | 117,004 | |
Total assets, Fair value | 123,735 | | 117,004 | |
Level 2 | Recurring | Money market funds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 0 | | 0 | |
Level 2 | Recurring | Certificates of deposit | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | 0 | | 0 | |
Level 2 | Recurring | U.S. agency notes | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 54,261 | | 50,540 | |
Level 2 | Recurring | Commercial paper | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 7,997 | | 4,999 | |
Level 2 | Recurring | Corporate bonds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | 61,477 | | 61,465 | |
Level 3 | Recurring | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | ' | [1] | ' | [1] |
Total investments | ' | | ' | |
Total assets, Fair value | ' | | ' | |
Level 3 | Recurring | Money market funds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | ' | | ' | |
Level 3 | Recurring | Certificates of deposit | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total cash equivalents and certificates of deposit | ' | | ' | |
Level 3 | Recurring | U.S. agency notes | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | ' | | ' | |
Level 3 | Recurring | Commercial paper | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | ' | | ' | |
Level 3 | Recurring | Corporate bonds | ' | | ' | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ' | | ' | |
Total investments | ' | | ' | |
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[1] | Includes an immaterial amount of restricted cash as of September 30, 2014 and $0.6 million of restricted cash as of December 31, 2013 and excludes $29.5 million and $21.6 million of operating cash balances as of September 30, 2014 and December 31, 2013, respectively. |