SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Foreign currency transaction gains and losses	$ 1,259	$ 2,483	$ 48
Ownership interest in a limited partnership investment fund (in hundredths)	6.00%
Impairment charges	0	774
Impairment of investment in limited partnership investment fund	0	1,347
Sales price of long-lived assets held for sale	5,752
Commissions and closing costs on sale of long-lived assets held for sale	247
Long Lived Assets Held-for-sale, Proceeds from Sale	5,508
Finite-Lived Intangible Asset, Weighted Average Period before Next Renewal or Extension Beginning	1 year
Finite-Lived Intangible Asset, Weighted Average Period before Next Renewal or Extension Ending	12 years
Goodwill impairment	0
Impairment of Long-Lived Assets Held-for-use	1,710	348
Amortization of software development costs	522	695	695
Amount capitalized for internal-use software	364	0
Accumulated amortization of internal-use software	819
Advertising costs recorded	2,031	641	1,182
Requisite service period	4 years
Components of accumulated other comprehensive income, net of tax [Abstract]
Foreign currency translation adjustment	5,374	821
Unrealized gains on available-for-sale and non-marketable securities	896	845
Unrealized gains on cash flow hedges	32	826
Accumulated other comprehensive income, net of tax	$ 6,302	$ 2,492
Securities excluded from diluted earnings per common share [Abstract]
Securities excluded from diluted earnings per common share (in shares)	19,944	12,106	11,758
Employee stock options [Member]
Securities excluded from diluted earnings per common share [Abstract]
Securities excluded from diluted earnings per common share (in shares)	6,101	6,276	6,636
Employee stock purchase plan [Member]
Securities excluded from diluted earnings per common share [Abstract]
Securities excluded from diluted earnings per common share (in shares)	210	64	0
Restricted stock and restricted stock units [Member]
Securities excluded from diluted earnings per common share [Abstract]
Securities excluded from diluted earnings per common share (in shares)	3,734	2,597	1,953
Convertible notes [Member]
Securities excluded from diluted earnings per common share [Abstract]
Securities excluded from diluted earnings per common share (in shares)	9,899	3,169	3,169