Investments and Fair Value Measurements (Details) (USD $)	3 Months Ended		49 Months Ended
	Mar. 31, 2012 days	Mar. 31, 2011	Mar. 31, 2012	Feb. 14, 2008	Mar. 31, 2012 Minimum [Member] years	Dec. 31, 2011 Minimum [Member] years	Dec. 31, 2010 Minimum [Member]	Mar. 31, 2012 Maximum [Member] years	Dec. 31, 2011 Maximum [Member] years	Dec. 31, 2010 Maximum [Member]	Mar. 31, 2012 Available-for-sale Securities [Member]	Mar. 31, 2012 Auction rate student loan educational bonds long-term	Dec. 31, 2011 Auction rate student loan educational bonds long-term
Schedule of Available-for-sale Securities
Held-to-maturity Securities	$ 1,300,000		$ 1,300,000
Amortized Cost and Fair Value of Investments
Amortized Cost				198,500,000							53,625,000	53,625,000	53,650,000
Gross Unrealized Gains												0	0
Gross Unrealized Losses												3,081,000	3,081,000
Fair Value											50,544,000	50,544,000	50,569,000
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	50,544,000		50,544,000
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	53,625,000		53,625,000
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	50,569,000	88,694,000
Settlements	(25,000)	(15,425,000)
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	0
Fair value, end of period	50,544,000	73,269,000	50,544,000
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	(25,000)	(15,425,000)
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
Investment Inputs Average Life of Underlying Loans					2	2		12	12
Investment Inputs Rate of Return					0.55%		0.68%	2.93%		2.92%
Investment Inputs Discount Rate					0.38%		0.48%	1.21%		1.14%
Investment Inputs Liquidity Discount Rate					0.35%		0.55%	1.01%		1.16%
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities			$ 144,800,000