Cash Equivalents and Short-Term Investments - Cash Equivalents and Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Cash equivalents:
Money market accounts, Cost	$ 8,354	$ 5,349
Short-term investments:
Variable rate demand notes, Cost	15,105	15,105
Total, Cost	23,459	20,454
Cash equivalents:
Money market accounts, Fair Market Value	8,354	5,349
Short-term investments:
Variable rate demand notes, Fair Market Value	15,105	15,105
Total, Fair Market Value	$ 23,459	$ 20,454