Cash, Cash Equivalents and Investments - Additional Information (Detail) (USD $)	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
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%
Cash deposited in the US banks insured by the Federal Deposit Insurance Corporation	$ 250,000
Cash	16,789,000	13,043,000
Cash equivalents	631,000	4,500,000
Cash and cash equivalents in foreign bank	800,000	800,000
Short-term investments	37,516,000	33,596,000
Certificates of deposit	6,493,000	5,062,000
Net unrealized gains	13,000
Long-term investments	0
Percentage of investment in bond protected by bond default insurance	8.00%
Minimum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments, maturities	90 days
Maximum [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments, maturities	1 year
Money market funds and other cash equivalents [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	14,678,000	10,162,000
Corporate debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	7,782,000	9,880,000
U.S. government agency bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Short-term investments	$ 8,576,000	$ 8,498,000