Fair Values on Financial Assets and Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair value of financial assets and liabilities
Total financial assets	$ 80,942	$ 96,163
Level 1
Fair value of financial assets and liabilities
Total financial assets	4,592	70,465
Level 2
Fair value of financial assets and liabilities
Total financial assets	76,350	25,698
Money market funds
Fair value of financial assets and liabilities
Total financial assets	105	59,302
Money market funds | Level 1
Fair value of financial assets and liabilities
Total financial assets	105	59,302
United States government agency securities
Fair value of financial assets and liabilities
Total financial assets	18,982
United States government agency securities | Level 2
Fair value of financial assets and liabilities
Total financial assets	18,982
Corporate debt securities
Fair value of financial assets and liabilities
Total financial assets	57,368	25,698
Corporate debt securities | Level 2
Fair value of financial assets and liabilities
Total financial assets	57,368	25,698
Marketable equity securities
Fair value of financial assets and liabilities
Total financial assets	4,487	11,163
Marketable equity securities | Level 1
Fair value of financial assets and liabilities
Total financial assets	$ 4,487	$ 11,163