SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $)	3 Months Ended
	Mar. 31, 2014 objective	Mar. 31, 2013	Dec. 31, 2013
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Restricted cash	$ 0		$ 0
Number of objectives of the entity's investment strategy	2
Minimum contractual term of certain current investments which can be liquidated	1 year
Realized losses	0	0
Realized gains	6,300	2,200
Available-for-sale securities
Amortized Cost	98,071,000		120,283,000
Gains in Accumulated Other Comprehensive Income	133,000		125,000
Estimated Fair Value	98,204,000		120,408,000
U.S. government agency securities
Available-for-sale securities
Amortized Cost	29,662,000		34,291,000
Gains in Accumulated Other Comprehensive Income	48,000		47,000
Estimated Fair Value	29,710,000		34,338,000
Corporate bonds
Available-for-sale securities
Amortized Cost	61,857,000		77,935,000
Gains in Accumulated Other Comprehensive Income	83,000		75,000
Estimated Fair Value	61,940,000		78,010,000
Certificates of deposit
Available-for-sale securities
Amortized Cost	5,052,000		6,558,000
Gains in Accumulated Other Comprehensive Income	2,000		3,000
Estimated Fair Value	5,054,000		6,561,000
Commercial paper
Available-for-sale securities
Amortized Cost	1,500,000		1,499,000
Estimated Fair Value	$ 1,500,000		$ 1,499,000