Fair Value Measurements - Assets and Liabilities Carried at Fair Value and Measured on Recurring Basis (Detail) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Assets:
Total	$ 19,967	$ 61,276
Liabilities:
Total liabilities	1,496	1,180
Business Acquisition Contingent Consideration Current [Member]
Liabilities:
Total liabilities	568
Business Acquisition Contingent Consideration Non Current [Member]
Liabilities:
Total liabilities	928	1,180
Money Market Funds [Member]
Assets:
Total	1,607	33,345
Short-term Investments [Member]
Assets:
Total	14,401	6,610
Long-term Investments [Member]
Assets:
Total	3,959	21,321
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets:
Total	1,607	33,345
Liabilities:
Total liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Business Acquisition Contingent Consideration Current [Member]
Liabilities:
Total liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Business Acquisition Contingent Consideration Non Current [Member]
Liabilities:
Total liabilities
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Money Market Funds [Member]
Assets:
Total	1,607	33,345
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Short-term Investments [Member]
Assets:
Total
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Long-term Investments [Member]
Assets:
Total
Significant Other Observable Inputs (Level 2) [Member]
Assets:
Total	18,360	27,931
Liabilities:
Total liabilities
Significant Other Observable Inputs (Level 2) [Member] | Business Acquisition Contingent Consideration Current [Member]
Liabilities:
Total liabilities
Significant Other Observable Inputs (Level 2) [Member] | Business Acquisition Contingent Consideration Non Current [Member]
Liabilities:
Total liabilities
Significant Other Observable Inputs (Level 2) [Member] | Money Market Funds [Member]
Assets:
Total
Significant Other Observable Inputs (Level 2) [Member] | Short-term Investments [Member]
Assets:
Total	14,401	6,610
Significant Other Observable Inputs (Level 2) [Member] | Long-term Investments [Member]
Assets:
Total	3,959	21,321
Significant Unobservable Inputs (Level 3) [Member]
Assets:
Total
Liabilities:
Total liabilities	1,496	1,180
Significant Unobservable Inputs (Level 3) [Member] | Business Acquisition Contingent Consideration Current [Member]
Liabilities:
Total liabilities	568
Significant Unobservable Inputs (Level 3) [Member] | Business Acquisition Contingent Consideration Non Current [Member]
Liabilities:
Total liabilities	928	1,180
Significant Unobservable Inputs (Level 3) [Member] | Money Market Funds [Member]
Assets:
Total
Significant Unobservable Inputs (Level 3) [Member] | Short-term Investments [Member]
Assets:
Total
Significant Unobservable Inputs (Level 3) [Member] | Long-term Investments [Member]
Assets:
Total