Investments and Fair Value Measurements (Details) (USD $)	12 Months Ended			46 Months Ended
	Dec. 31, 2011 days	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011	Feb. 14, 2008
Amortized Cost and Fair Value of Investments
Amortized Cost					$ 198,500,000
Fair Value	50,600,000	88,700,000		50,600,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value	0			0
Available-for-sale Securities, Debt Maturities, within One Year, Amortized Cost Basis	0			0
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Fair Value	0			0
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Amortized Cost Basis	0			0
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Fair Value	0			0
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	0			0
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	50,569,000			50,569,000
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	53,650,000			53,650,000
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	88,694,000	147,419,000
Settlements	(38,125,000)	(61,225,000)
Purchases	0	0
Issuances	0	0
Sales	0	0
Transfers in to (out of) Level 3	0	0
Total gains or losses (realized/unrealized) included in earnings	0	0
Total gains or losses (realized/unrealized) included in other comprehensive loss, net of tax	0	2,500,000
Fair value, end of period	50,569,000	88,694,000	147,419,000	50,569,000
Auction Rate Securities, Debt, Rate Setting Interval (in days)	35
Percent of portfolio with AAA credit rating	100.00%			100.00%
Maturity and calls of investments	(38,125,000)	(61,225,000)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(3,100,000)			(3,100,000)
Basis of Tested Impact on Securities	0.50%			0.50%
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	0	0	0
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	38,100,000			144,800,000
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Investment Inputs Average Life of Underlying Loans	2	2		2
Investment Inputs Rate of Return	0.68%	1.28%		0.68%
Investment Inputs Discount Rate	0.48%	0.53%		0.48%
Investment Inputs Liquidity Discount Rate	0.55%	0.40%		0.55%
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Investment Inputs Average Life of Underlying Loans	12	12		12
Investment Inputs Rate of Return	2.92%	4.12%		2.92%
Investment Inputs Discount Rate	1.14%	1.85%		1.14%
Investment Inputs Liquidity Discount Rate	1.16%	0.80%		1.16%
Auction rate student loan educational bonds current
Amortized Cost and Fair Value of Investments
Amortized Cost	0	8,300,000		0
Gross Unrealized Gains	0	0		0
Gross Unrealized Losses	0	0		0
Fair Value	0	8,300,000		0
Auction rate student loan eductional bonds current total
Amortized Cost and Fair Value of Investments
Amortized Cost	0	8,300,000		0
Gross Unrealized Gains	0	0		0
Gross Unrealized Losses	0	0		0
Fair Value	0	8,300,000		0
Auction rate student loan educational bonds long-term
Amortized Cost and Fair Value of Investments
Amortized Cost	53,650,000	83,475,000		53,650,000
Gross Unrealized Gains	0	0		0
Gross Unrealized Losses	3,081,000	3,081,000		3,081,000
Fair Value	50,569,000	80,394,000		50,569,000
Auction rate student loan eductional bonds long-term total
Amortized Cost and Fair Value of Investments
Amortized Cost	53,650,000	83,475,000		53,650,000
Gross Unrealized Gains	0	0		0
Gross Unrealized Losses	3,081,000	3,081,000		3,081,000
Fair Value	50,569,000	80,394,000		50,569,000
Auction rate student loan educational bonds total
Amortized Cost and Fair Value of Investments
Amortized Cost	53,650,000	91,775,000		53,650,000
Gross Unrealized Gains	0	0		0
Gross Unrealized Losses	3,081,000	3,081,000		3,081,000
Fair Value	$ 50,569,000	$ 88,694,000		$ 50,569,000