FAIR VALUE MEASUREMENTS (Details) (USD $) In Thousands, unless otherwise specified																															12 Months Ended
	Dec. 31, 2011 Estimate of Fair Value, Fair Value Disclosure [Member]	Dec. 31, 2010 Estimate of Fair Value, Fair Value Disclosure [Member]	Dec. 31, 2011 Estimate of Fair Value, Fair Value Disclosure [Member] Commercial paper [Member]	Dec. 31, 2010 Estimate of Fair Value, Fair Value Disclosure [Member] Commercial paper [Member]	Dec. 31, 2011 Estimate of Fair Value, Fair Value Disclosure [Member] Money market funds [Member]	Dec. 31, 2010 Estimate of Fair Value, Fair Value Disclosure [Member] Money market funds [Member]	Dec. 31, 2011 Estimate of Fair Value, Fair Value Disclosure [Member] Certificates of deposit [Member]	Dec. 31, 2010 Estimate of Fair Value, Fair Value Disclosure [Member] U.S. Government debt securities [Member]	Dec. 31, 2011 Estimate of Fair Value, Fair Value Disclosure [Member] Corporate securities [Member]	Dec. 31, 2010 Estimate of Fair Value, Fair Value Disclosure [Member] Corporate securities [Member]	Dec. 31, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]	Dec. 31, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Commercial paper [Member]	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Commercial paper [Member]	Dec. 31, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Money market funds [Member]	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Money market funds [Member]	Dec. 31, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Certificates of deposit [Member]	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] U.S. Government debt securities [Member]	Dec. 31, 2011 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Corporate securities [Member]	Dec. 31, 2010 Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] Corporate securities [Member]	Dec. 31, 2011 Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member]	Dec. 31, 2011 Significant Other Observable Inputs (Level 2) [Member] Commercial paper [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member] Commercial paper [Member]	Dec. 31, 2011 Significant Other Observable Inputs (Level 2) [Member] Money market funds [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member] Money market funds [Member]	Dec. 31, 2011 Significant Other Observable Inputs (Level 2) [Member] Certificates of deposit [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member] U.S. Government debt securities [Member]	Dec. 31, 2011 Significant Other Observable Inputs (Level 2) [Member] Corporate securities [Member]	Dec. 31, 2010 Significant Other Observable Inputs (Level 2) [Member] Corporate securities [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Obligations, fair value																					$ 0
Cash and Cash Equivalents, Fair Value Disclosure			9,849	7,135	30,190	52,951	10,000						0	0	30,190	52,951	0						9,849	7,135	0	0	10,000
Investments, Fair Value Disclosure								6,100	62,940	54,523								0	0	0								6,100	62,940	54,523
Assets, Fair Value Disclosure	112,979	120,709									30,190	52,951									82,789	67,758
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance																															0
Purchases and issuances																															3,000
Settlements																															(3,000)
Ending balance																															$ 0