Notes Payable Convertible Senoir Notes Due 2015 (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	16,000,000
Investment Warrants, Exercise Price	$ 16.00
Warrants, Deliverable	11,600,000
Proceeds from Issuance of Warrants	$ 0	$ 0	$ 15,600,000
Convertible Debt Issued in 2010 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Effective Percentage	8.90%
Principal Amount of Convertible Senior Notes Payable at Issuance	200,000,000
Debt Instrument, Interest Rate, Stated Percentage	3.50%
Deferred Finance Costs, Gross	6,800,000
Number of Days Holders May Convert	5
Measurement Period of Convertible Senior Notes	10
Debt Instrument, Face Amount	1,000
Product of Last Reported Common Stock Sale Price and Conversion Rate	98.00%
Number of Days to Measure Stock Value Against Conversion Value	20
Consecutive Trading Day Period to Determine Convertibility	30
Stock Price Must Exceed Conversion Price to Allow Conversion	130.00%
Debt Instrument, Convertible, Conversion Price	$ 12.35		$ 12.50
Debt Instrument, Convertible, Number of Equity Instruments, Shares	80.9486		80
Debt Instrument, Convertible, Fundamental Change Stock Price Floor	10.00
Debt Instrument, Convertible, Conversion Rate Increase Upon Fundamental Change	20
2015 Notes Embedded Conversion Derivative [Member]
Debt Instrument [Line Items]
Derivative, Liability, Fair Value at Issuance	37,000,000
Derivative instruments	43,100,000	45,600,000
2015 Notes Hedges [Member]
Debt Instrument [Line Items]
Derivative, Asset, Fair Value, Issuance	37,000,000
Derivative Liability, Fair Value, Gross Liability	$ 43,100,000	$ 45,600,000
Derivative, Conversion Spread, Shares	16,000,000
Derivative, Asset, Strike Price	$ 12.50