Investments and Fair Value Measurements (Details) (USD $)	3 Months Ended		6 Months Ended		64 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Dec. 31, 2012	Feb. 14, 2008
Schedule of Available-for-sale Securities
Basis of Tested Impact on Securities	0.50%		0.50%		0.50%
Held-to-maturity Securities	$ 1,400,000		$ 1,400,000		$ 1,400,000	$ 1,300,000
Amortized Cost and Fair Value of Investments
Amortized Cost							198,500,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available-for-sale Securities, Debt Maturities, within One Year, Fair Value	0		0		0
Available-for-sale Securities, Debt Maturities, within One Year, Amortized Cost Basis	0		0		0
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Fair Value	0		0		0
Available-for-sale Securities, Debt Maturities, after One Through Five Years, Amortized Cost Basis	0		0		0
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Fair Value	0		0		0
Available-for-sale Securities, Debt Maturities, after Five Through Ten Years, Amortized Cost Basis	0		0		0
Available-for-sale Securities, Debt Maturities, after Ten Years, Fair Value	10,791,000		10,791,000		10,791,000
Available-for-sale Securities, Debt Maturities, after Ten Years, Amortized Cost Basis	11,475,000		11,475,000		11,475,000
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning of period			20,016,000	50,569,000
Settlements			(9,825,000)	(31,325,000)
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 income, net of tax			600,000	1,797,000
Fair value, end of period	10,791,000	21,041,000	10,791,000	21,041,000	10,791,000
Percent of portfolio with AAA credit rating	70.00%		70.00%		70.00%
Maturity and calls of investments			(9,825,000)	(31,325,000)
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(700,000)		(700,000)		(700,000)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	600,000	1,797,000	600,000	1,797,000
Available-for-sale Securities, Gross Realized Gain (Loss)	0	0	0	0
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	9,800,000		9,825,000	31,325,000	187,000,000
Auction rate security investments percentage of total assets	2.10%		2.10%		2.10%	4.30%
Available-for-sale Securities [Member]
Amortized Cost and Fair Value of Investments
Amortized Cost	11,475,000		11,475,000		11,475,000
Fair Value	10,791,000		10,791,000		10,791,000
Auction rate student loan educational bonds long-term
Amortized Cost and Fair Value of Investments
Amortized Cost	11,475,000		11,475,000		11,475,000	21,300,000
Gross Unrealized Gains	0		0		0	0
Gross Unrealized Losses	684,000		684,000		684,000	1,284,000
Fair Value	$ 10,791,000		$ 10,791,000		$ 10,791,000	$ 20,016,000