INVESTMENTS (DETAILS) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Available For Sale Securities Balance Sheet Reported Amounts Abstract
Available For Sale Securities Current	$ 245,500,000
Available For Sale Securities Noncurrent	40,300,000
Schedule Of Available For Sale Securities [Line Items]
Available For Sale Debt Securities Amortized Cost Basis	290,573,000	512,491,000
Available For Sale Securities Gross Unrealized Gains	382,000	1,413,000
Available For Sale Securities Gross Unrealized Losses	(5,188,000)	(7,232,000)
Other Than Temporary Impairment Losses Investments Available For Sale Securities	0	0
Available For Sale Securities Fair Value Disclosure	285,767,000	506,672,000
Available For Sale Securities Continuous Unrealized Loss Position Fair Value Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	134,333,000
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	12,793,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	581,000
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	4,607,000
Available For Sale Securities Gross Realized Gain Loss Abstract
Available For Sale Securities Gross Realized Gains	500,000	0	1,600,000
Available For Sale Securities Gross Realized Losses	600,000	700,000	0
Other Comprehensive Income Available For Sale Securities Adjustment Before Tax Period Increase Decrease	600,000	1,200,000	5,900,000
Available For Sale Securities Debt Maturities Amortized Cost Abstract
Available For Sale Securities Debt Maturities Within One Year Amortized Cost	98,334,000
Available For Sale Securities Debt Maturities After One Through Five Years Amortized Cost	174,839,000
Available For Sale Securities Debt Maturities After Ten Years Amortized Cost	17,400,000
Available For Sale Securities Debt Maturities Fair Value Abstract
Available For Sale Securities Debt Maturities Within One Year Fair Value	98,374,000
Available For Sale Securities Debt Maturities After One Through Five Years Fair Value	174,600,000
Available For Sale Securities Debt Maturities After Ten Years Fair Value	12,793,000
Available For Sale Securities Other Disclosure Items Abstract
Other Than Temporary Impairment Loss Recognized	0	260,000	(33,000)
Gain On Sale Of Investments			1,500,000
Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available For Sale Debt Securities Amortized Cost Basis	138,554,000	145,758,000
Available For Sale Securities Gross Unrealized Gains	161,000	454,000
Available For Sale Securities Gross Unrealized Losses	(549,000)	(48,000)
Other Than Temporary Impairment Losses Investments Available For Sale Securities	0	0
Available For Sale Securities Fair Value Disclosure	138,166,000	146,164,000
Available For Sale Securities Continuous Unrealized Loss Position Fair Value Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	80,470,000
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	549,000
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	0
US Treasury And Government [Member]
Schedule Of Available For Sale Securities [Line Items]
Available For Sale Debt Securities Amortized Cost Basis	125,092,000	328,262,000
Available For Sale Securities Gross Unrealized Gains	221,000	953,000
Available For Sale Securities Gross Unrealized Losses	(24,000)	(88,000)
Other Than Temporary Impairment Losses Investments Available For Sale Securities	0	0
Available For Sale Securities Fair Value Disclosure	125,289,000	329,127,000
Available For Sale Securities Continuous Unrealized Loss Position Fair Value Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	44,344,000
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	24,000
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	0
Auction Rate Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available For Sale Debt Securities Amortized Cost Basis	17,400,000	28,575,000
Available For Sale Securities Gross Unrealized Gains	0	0
Available For Sale Securities Gross Unrealized Losses	(4,607,000)	(7,095,000)
Other Than Temporary Impairment Losses Investments Available For Sale Securities	0	0
Available For Sale Securities Fair Value Disclosure	12,793,000	21,480,000
Available For Sale Securities Continuous Unrealized Loss Position Fair Value Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	12,793,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	4,607,000
Asset Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Available For Sale Debt Securities Amortized Cost Basis	9,527,000	9,896,000
Available For Sale Securities Gross Unrealized Gains	0	6,000
Available For Sale Securities Gross Unrealized Losses	(8,000)	(1,000)
Other Than Temporary Impairment Losses Investments Available For Sale Securities	0	0
Available For Sale Securities Fair Value Disclosure	9,519,000	9,901,000
Available For Sale Securities Continuous Unrealized Loss Position Fair Value Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months Fair Value	9,519,000
Available For Sale Securities Continuous Unrealized Loss Position Twelve Months Or Longer Fair Value	0
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Abstract
Available For Sale Securities Continuous Unrealized Loss Position Less Than 12 Months Aggregate Losses	8,000
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses	$ 0