Long-Term Obligations and Commitments, Long-Term Obligations (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Long-Term Obligations [Abstract]
Total long-term obligations, including current portion	$ 472,648	$ 457,782
Less: current portion	(515)	(2,882)
Total Long-Term Obligations	472,133	454,900
Convertible Senior Notes [Member] | 1 Percent Convertible Senior Notes [Member]
Long-Term Obligations [Abstract]
Total long-term obligations, including current portion	347,214	327,486
Convertible Senior Notes [Member] | 2 3/4 Percent Convertible Senior Notes [Member]
Long-Term Obligations [Abstract]
Total long-term obligations, including current portion	50,361	48,014
Long-term Financing Liability for Leased Facility [Member]
Long-Term Obligations [Abstract]
Total long-term obligations, including current portion	72,217	71,731
Equipment Financing Arrangement [Member]
Long-Term Obligations [Abstract]
Total long-term obligations, including current portion	515	3,226
Leases and Other Obligations [Member]
Long-Term Obligations [Abstract]
Total long-term obligations, including current portion	$ 2,341	$ 7,325