Cash, Cash Equivalents and Investments - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents maturities	90 days	90 days
Investment of cash equivalents are redeemable upon demand using amortized cost method	$ 1.00
Investment in money market funds restricted by investment in short term securities, percentage	100.00%
Cash	$ 6,116,000	$ 7,507,000
Cash equivalents	8,844,000	7,348,000
Cash and cash equivalents in foreign bank	1,700,000	900,000
Short-term investments	$ 18,002,000	18,456,000
Short-term investments, maturities	90 days
Net unrealized gains (losses)	$ 10,000	$ 9,000
Percentage of investment in bond protected by bond default insurance	7.00%	6.00%
Pre-refunded Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 300,000
Short-term investments	8,800,000	$ 7,800,000
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	5,800,000	3,600,000
Short-term investments	4,400,000	5,600,000
U.S. Government Agency Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	2,100,000	2,800,000
Short-term investments	2,800,000	2,600,000
Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	400,000	800,000
Short-term investments	2,000,000	2,500,000
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	200,000	100,000
China [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash in foreign bank	1,300,000	$ 500,000
Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Federal Deposit Insurance Corporation insured limit	$ 250,000