Convertible Notes - Debt Instruments (Details) (USD $)	12 Months Ended			3 Months Ended	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 Convertible Subordinated Debt [Member]	Dec. 31, 2011 Convertible Subordinated Debt [Member]
Debt Instrument [Line Items]
Debt instrument, issuance date					May 19, 2006
Debt instrument, face amount at issuance				$ 115,000,000	$ 115,000,000
Debt instrument, effective interest rate					2.875%
Debt instrument, maturity date					Jun. 01, 2013
Debt instrument, issuance costs					3,100,000
Debt instrument, amortization of issuance costs				100,000
Convertible debt	89,011,000	89,012,000		89,000,000	89,000,000
Debt conversion, amount					$ 1,000
Shares issued during period for debt conversion					34
Incremental common shares attributable to conversion of debt securities	3,033,000	3,223,000	0		3,032,743
Debt instrument, conversion price				$ 29.35	$ 29.35