CASH, CASH EQUIVALENTS, AND MARKETABLE SECURITIES (Details) (USD $)					9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011 security	Sep. 30, 2011	Dec. 31, 2010	Sep. 30, 2012 Maximum	Sep. 30, 2012 Available-for-sale securities	Dec. 31, 2011 Available-for-sale securities	Sep. 30, 2012 Money market funds	Dec. 31, 2011 Money market funds	Sep. 30, 2012 U.S. corporate debt securities	Dec. 31, 2011 U.S. corporate debt securities	Sep. 30, 2012 Debt securities issued by U.S. government and U.S. government agencies	Dec. 31, 2011 Debt securities issued by U.S. government and U.S. government agencies	Sep. 30, 2012 Marketable equity securities	Dec. 31, 2011 Marketable equity securities
Cash, cash equivalents, and marketable securities
Amortized Cost	$ 124,947,000	$ 112,926,000						$ 1,041,000	$ 4,469,000	$ 34,666,000	$ 32,830,000	$ 89,224,000	$ 72,901,000	$ 16,000	$ 2,726,000
Gross Unrealized Gains	39,000	14,000								2,000		22,000	14,000	15,000
Gross Unrealized Losses	(1,000)	(910,000)									(1,000)	(1,000)	(2,000)		(907,000)
Fair Value	124,985,000	112,030,000				124,985,000	112,030,000	1,041,000	4,469,000	34,668,000	32,829,000	89,245,000	72,913,000	31,000	1,819,000
Amounts included in cash and cash equivalents	26,772,000	39,788,000	37,939,000	25,554,000		21,889,000	23,767,000
Marketable securities, current	103,065,000	86,444,000				103,065,000	86,444,000
Marketable securities, non-current	31,000	1,819,000				31,000	1,819,000
Maturity period of debt securities					1 year
Equity Investments
Number of equity investments carried at cost		1
Carrying amount of non-marketable security		$ 500,000