Convertible Notes (Interest Expense) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest expense related to notes
Total interest expense on convertible notes	$ 32,885	$ 27,510	$ 24,828
Convertible notes
Interest expense related to notes
Total interest expense on convertible notes	28,504	23,320	21,247
Convertible notes | 1.125% Convertible Senior Notes due 2018
Interest expense related to notes
Coupon interest	582	0	0
Amortization of discount at an additional effective interest rate	2,171	0	0
Additional Effective Interest Rate	5.50%
Convertible notes | 5% Convertible Senior Notes due 2014
Interest expense related to notes
Coupon interest	8,625	8,625	8,625
Amortization of discount at an additional effective interest rate	$ 17,126	$ 14,695	$ 12,622
Additional Effective Interest Rate	11.70%	11.70%	11.70%