Long-Term Debt (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
2.25% Convertible Senior Notes due 2036 [Member]
Contractual interest expense and the discount amortization
Year-to-date contractual interest expense	$ 1,028		$ 1,028
Year-to-date discount amortization	2,012	[1]	1,826	[1]
Effective interest rate of liability component	7.70%		7.70%
3.00% Convertible Senior Notes due 2020 [Member]
Contractual interest expense and the discount amortization
Year-to-date contractual interest expense	863		863
Year-to-date discount amortization	$ 899	[2]	$ 785	[2]
Effective interest rate of liability component	8.60%		8.60%

[1] Represents the incremental impact of the accounting for convertible debt as primarily codified in ASC 470, Debt.

[2] Represents the incremental impact of the accounting for convertible debt as primarily codified in ASC 470, Debt