Long-Term Debt (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
2.25% Convertible Notes due 2036
Contractual interest expense and the discount amortization
Year-to-date contractual interest expense	$ 4,112	$ 4,112	$ 4,119
Year-to-date discount amortization	7,530	6,948	6,409
Effective interest rate of liability component	7.70%	7.70%	7.70%
3.00% Convertible Notes due 2020
Contractual interest expense and the discount amortization
Year-to-date contractual interest expense	3,450	3,450	3,461
Year-to-date discount amortization	$ 3,251	$ 2,966	$ 2,706
Effective interest rate of liability component	8.60%	8.60%	8.60%