Accounting Policies (Details 2) (USD $)	3 Months Ended								12 Months Ended			0 Months Ended	1 Months Ended		12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Nov. 15, 2011 3 7/8% Convertible Senior Notes due 2011 upon maturity	Nov. 30, 2011 3 7/8% Convertible Senior Notes due 2011 upon maturity	Nov. 30, 2011 Adoption of FASB guidance relating to convertible debt instruments that may be settled in cash upon conversion 3 7/8% Convertible Senior Notes due 2011 upon maturity	Dec. 31, 2011 Adjustment Adoption of FASB guidance relating to convertible debt instruments that may be settled in cash upon conversion	Dec. 31, 2010 Adjustment Adoption of FASB guidance relating to convertible debt instruments that may be settled in cash upon conversion
Accounting Policies
Decrease in net income on adoption of FASB guidance	$ (86,267,000)	$ (111,882,000)	$ (74,025,000)	$ (90,626,000)	$ (192,948,000)	$ (102,885,000)	$ (19,676,000)	$ (48,984,000)	$ (362,800,000)	$ (364,493,000)	$ (246,167,000)				$ (4,000,000)	$ (4,200,000)
Decrease in net income per diluted share on adoption of FASB guidance (in dollars per share)	$ (0.29)	$ (0.38)	$ (0.25)	$ (0.31)	$ (0.66)	$ (0.35)	$ (0.11)	$ (0.30)	$ (1.23)	$ (1.58)	$ (1.56)				$ (0.02)	$ (0.03)
Principal amount repaid												$ 230,000,000		$ 230,000,000
Aggregate shares of common stock issued for the conversion value in excess of the principal amount												943,714	943,714	943,714