Long-Term Obligations (Details) (USD $)	Sep. 30, 2013	Dec. 31, 2012
Long-Term Obligations [Line Items]
5% Convertible Senior Notes due October 2017, interest payable semi-annually in April and October, beginning April 1, 2013	$ 130,000,000	$ 130,000,000
Total long-term obligations	149,147,000	154,642,000
Less current portion	(7,631,000)	(7,601,000)
Non-current portion	141,516,000	147,041,000
Convertible Notes Payable
Long-Term Obligations [Line Items]
5% Convertible Senior Notes due October 2017, interest payable semi-annually in April and October, beginning April 1, 2013	130,000,000	130,000,000
Unamortized debt issuance expense	4,300,000	5,000,000
Loan Agreement
Long-Term Obligations [Line Items]
Bank loans due May 2015, principal and interest payable monthly, weighted-average effective interest rate of 5.5%; net of unamortized discounts of $153 and $326 at September 30, 2013 and December 31, 2012, respectively	12,669,000	17,949,000
Financing Lease Obligations
Long-Term Obligations [Line Items]
Obligation for building and improvements, effective interest of 4.9% at September 30, 2013 and December 31, 2012, expiring October 2026	6,176,000	6,318,000
Capital Lease Obligations
Long-Term Obligations [Line Items]
Capital lease liabilities expiring January 2016, net of unamortized discounts of $71 and $117 at September 30, 2013 and December 31, 2012, respectively	$ 302,000	$ 375,000