Debt and Capital Lease Obligations (Current and Long-Term Debt Balances) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Oct. 31, 2012
Current
Capital Lease Obligation	$ 46	$ 580
Small Land Purchase	0	77
Total debt balances, Current	46	657
Long-Term
Capital Lease Obligation	0	0
Small Land Purchase	0	0
Total debt balances, Long-Term	$ 259,661	$ 255,099
1.75% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.75%	1.75%	1.75%	1.75%
Current
Debt, Current	$ 0	$ 0
Long-Term
Aggregate principal	335,150	335,150
Debt discount	(72,409)	(76,754)
Deferred debt issue costs	(3,604)	(3,821)
Debt balance	$ 259,137	$ 254,575
1.875% Convertible Debentures [Member]
Debt Instrument [Line Items]
Stated interest rate	1.875%	1.875%	1.875%
Current
Debt, Current	$ 0	$ 0
Long-Term
Aggregate principal	$ 524	$ 524