Long Term Debt (Convertible Senior Subordinated Notes) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Long-term debt outstanding	$ 161,852,000	$ 143,509,000
Payments on senior subordinated notes	100,000	111,766,000	2,933,000
Loss on early extinguishment of debt	0	0	79,000
Effective interest rate of nonconvertible debt	6.67%
Amortization of debt discount	0	3,903,000	4,244,000
Convertible Subordinated Debt [Member]
Debt Instrument [Line Items]
Long-term debt outstanding	227,000	327,000
Debt interest rate	2.50%	2.50%	2.50%
Payments on senior subordinated notes		111,800,000	2,900,000
Extinguishment of debt			3,000,000
Loss on early extinguishment of debt			100,000
Equity component at issuance	34,600,000
Principal value at issuance	150,000,000
Equity component at issuance, net of tax	21,800,000
Interest expense	$ 0	$ 2,500,000	$ 2,800,000