Debt (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Extinguishment of Debt [Line Items]
Cash Payments for Debt Conversions (in millions)	$ 13,215,000	$ 23,536,000
3.75% Senior Subordinated Convertible Notes, Due 2034
Extinguishment of Debt [Line Items]
Face Value of Debt Instrument (in millions)	88,000,000
Stated Interest Rate Percentage - Debt Instruments	3.75%
Maturity Date - Debt Instrument	Jan. 15, 2034
Excess above Principal Note Amount (in millions)	88,000,000
If Converted, Shares Issued	915,407
First Conversion Date	Jan. 15, 2009
Number of Notes Converted	29,760
Per Note Conversion Price	$ 449.17
Cash Payments for Debt Conversions (in millions)	32,400,000.0
Shares Issued for Convertible Debt	41,678
Weighted Average Share Price at Debt Conversion	94.50
Deferred Tax Liability (in millions)	$ 2,100,000.0