Cash, Cash Equivalents and Investments - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and cash equivalents maturities	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%
Federal Deposit Insurance Corporation Insured amount	$ 250,000
Cash	18,717,000	19,734,000
Cash equivalents	628,000	2,056,000
Cash and cash equivalents in foreign bank	1,200,000	1,000,000
Short-term investments	39,546,000	36,105,000
Short-term investments, maturities	90 days
Net unrealized gains	3,000
Percentage of investment in bond protected by bond default insurance	9.80%	5.00%
Pre-refunded Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	5,400,000	17,200,000
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	7,600,000	7,300,000
U.S. Government Agency Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	12,500,000	6,300,000
Certificates of Deposit [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	12,100,000	5,300,000
Mutual Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 1,900,000