Debt (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Mar. 12, 2008	Mar. 12, 2008 Senior Convertible Debentures [Member]	Jun. 30, 2011 Exempt Facility Revenue Bonds [Member]
Aggregate principal amount of senior convertible debentures	$ 166,500,000		$ 166,500,000		$ 181,500,000
Debt maturity date						Mar. 15, 2028	Jul. 01, 2020
Debt instrument interest rate						1.875%	8.00%
Common stock issuable on conversion of debt for $1000			42.5351
Debt conversion price	$ 23.51		$ 23.51
Convertible debentures exchanged for shares, value			15,000,000
Convertible debentures exchanged for shares, shares			1.84
Amortization expense related to issuance costs	246,000	245,000	491,000	490,000
Interest expense on the debentures	800,000	800,000	1,600,000	1,600,000
Cash payments for interest			1,600,000	1,600,000
Debt outstanding	30,000,000		30,000,000
Debt outstanding balance	29,500,000		29,500,000
Unamortized discount	500,000		500,000
Bridge capital loan commitment	$ 200,000,000		$ 200,000,000