Debt - Convertible Notes (Narrative) (Details) (Convertible Debt [Member], USD $)																			6 Months Ended		6 Months Ended
	Jun. 30, 2013 New 4.0% Notes [Member]		Dec. 31, 2012 New 4.0% Notes [Member]	Jun. 30, 2012 New 4.0% Notes [Member]		Jun. 30, 2013 New 4.25% Notes [Member]		Dec. 31, 2012 New 4.25% Notes [Member]	Jun. 30, 2012 New 4.25% Notes [Member]		Jun. 30, 2013 Original 4.0% Notes [Member]		Jun. 30, 2012 Original 4.0% Notes [Member]		Jun. 30, 2013 Original 4.25% Notes [Member]		Jun. 30, 2012 Original 4.25% Notes [Member]		Jun. 30, 2013 Total New Senior Convertible Notes [Member]	Mar. 31, 2011 Total New Senior Convertible Notes [Member]	Jun. 30, 2013 Weighted Average [Member] Total New Senior Convertible Notes [Member]
Debt Instrument [Line Items]
Principal amount	$ 105,322,000	[1]	$ 105,300,000	$ 105,322,000	[1]	$ 97,000,000	[1]	$ 97,000,000	$ 97,000,000	[1]	$ 9,600,000	[2]	$ 9,700,000	[2]	$ 3,000,000	[2]	$ 3,000,000	[2]
Unamortized debt discount and financing costs	$ 3,000,000		$ 4,400,000			$ 3,700,000		$ 4,900,000												$ 17,400,000
Debt instrument, effective interest rate																			6.73%
Debt instrument, remaining discount amortization period																					1 year 2 months 12 days

[1] Dilutive shares associated with the New Convertible Notes are attributable to the weighted average premium value, in shares, of the conversion shares underlying the New Convertible Notes in excess of the respective principal amounts thereof.

[2] Dilutive shares associated with the Original Convertible Notes are attributable to the underlying principal amounts.