Fair Value of Financial Instruments (Details) (USD $)	12 Months Ended				12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 13, 2006 Convertible Senior Subordinated Notes [Member]	Dec. 31, 2011 Debt Securities [Member]	Dec. 31, 2010 Debt Securities [Member]	Dec. 31, 2011 Equity Securities [Member]	Dec. 31, 2010 Equity Securities [Member]	Dec. 31, 2011 Preferred Stock Investments [Member]	Dec. 31, 2010 Preferred Stock Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Cost or Amortized Cost	$ 9,150,000	$ 9,150,000			$ 7,150,000	$ 7,150,000	$ 2,000,000	$ 2,000,000	$ 0	$ 0
Net Unrealized Gain (Loss)	(650,000)	(550,000)			(1,050,000)	(450,000)	400,000	(100,000)
Fair Value	8,500,000	8,600,000	13,100,000		6,100,000	6,700,000	2,400,000	1,900,000	0	0
Proceeds from sale of auction-rate security						4,300,000
Gain on sale of auction-rate security						900,000
Change in fair value of investments [Roll Forward]
Fair value at beginning of period	8,600,000	13,100,000			6,700,000	10,900,000	1,900,000	2,200,000	0	0
Temporary impairment credits (charges), net	(100,000)	(250,000)			(600,000)	50,000	500,000	(300,000)
Other-than-temporary impairment charges	0	(850,000)	(3,300,000)		0	(850,000)	0	0
Sale of security	0	(3,400,000)			0	(3,400,000)	0	0
Net change in fair value	(100,000)	(4,500,000)			(600,000)	(4,200,000)	500,000	(300,000)
Fair value at end of period	8,500,000	8,600,000	13,100,000		6,100,000	6,700,000	2,400,000	1,900,000	0	0
Debt Instrument [Line Items]
Interest rate (in hundredths)				2.4375%
Fair value of notes	$ 145,200,000	$ 150,200,000