FINANCIAL INSTRUMENTS AND FAIR VALUE MEASUREMENTS (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Fair value disclosure
Short-term investments	$ 35,960,000	$ 35,906,000
Restricted cash, cash equivalents, and short-term investments	1,903,000	1,902,000
Concentrations of Credit Risk of Financial Instruments
Cash, cash equivalents, and certificates of deposit which are not FDIC-insured	49,400,000	49,400,000
Fair value disclosure
Fair value disclosure
Cash and cash equivalents	95,728,000	105,354,000
Fair value disclosure | Cash deposits
Fair value disclosure
Cash and cash equivalents	54,880,000	63,547,000
Restricted cash, cash equivalents, and short-term investments	1,903,000	1,902,000
Fair value disclosure | Variable rate demand notes
Fair value disclosure
Cash and cash equivalents	29,747,000	29,706,000
Fair value disclosure | Money market funds
Fair value disclosure
Cash and cash equivalents	11,101,000	12,101,000
Fair value disclosure | Certificates of deposit
Fair value disclosure
Short-term investments	$ 35,960,000	$ 35,906,000