Investments and Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended		42 Months Ended
	Jul. 31, 2011	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011 days segments divisions locations	Jun. 30, 2010	Jul. 31, 2011	Feb. 14, 2008	Jun. 30, 2011 Auction rate student loan educational bonds current	Dec. 31, 2010 Auction rate student loan educational bonds current	Jun. 30, 2011 Auction rate student loan eductional bonds current total	Dec. 31, 2010 Auction rate student loan eductional bonds current total	Jun. 30, 2011 Auction rate student loan educational bonds long-term	Dec. 31, 2010 Auction rate student loan educational bonds long-term	Jun. 30, 2011 Auction rate student loan eductional bonds long-term total	Dec. 31, 2010 Auction rate student loan eductional bonds long-term total	Jun. 30, 2011 Auction rate student loan educational bonds total	Dec. 31, 2010 Auction rate student loan educational bonds total	Jun. 30, 2011 Minimum [Member] years	Dec. 31, 2010 Minimum [Member] years	Jun. 30, 2011 Maximum [Member] years	Dec. 31, 2010 Maximum [Member] years
Amortized Cost and Fair Value of Investments
Amortized Cost							$ 198,500	$ 2,550	$ 8,300	$ 2,550	$ 8,300	$ 67,575	$ 83,475	$ 67,575	$ 83,475	$ 70,125	$ 91,775
Gross Unrealized Gains								0	0	0	0	0	0	0	0	0	0
Gross Unrealized Losses								0	0	0	0	3,081	3,081	3,081	3,081	3,081	3,081
Fair Value								2,550	8,300	2,550	8,300	64,494	80,394	64,494	80,394	67,044	88,694
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis [Abstract]
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value		2,550		2,550
Available-for-sale Securities, Debt Maturities, within One Year, Amortized Cost Basis		2,550		2,550
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		64,494		64,494
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis		67,575		67,575
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period	67,044			88,694	147,419
Settlements				(21,650)	(26,450)
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		67,044	120,969	67,044	120,969
Auction Rate Securities, Debt, Rate Setting Interval (in days)				35
Percent of portfolio with AAA credit rating	100.00%	99.60%		99.60%		100.00%
Maturity and calls of investments	2,600	6,200		21,700		130,900
Basis of Tested Impact on Securities		0.50%		0.50%
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax		(3,081)		(3,081)
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds		$ 0	$ 0	$ 0	$ 0
Investment Inputs Average Life of Underlying Loans																		2	2	12	12
Investment Inputs Rate of Return																		0.95%	1.28%	3.84%	4.12%
Investment Inputs Discount Rate																		0.43%	0.53%	1.57%	1.85%
Investment Inputs Liquidity Discount Rate																		0.40%	0.40%	0.75%	0.80%