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Debt and Capital Lease Obligations (Current and Long-Term Debt Balances) (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Oct. 31, 2012
Current
Capital lease obligation	$ 0	$ 580
Small land purchase	0	77
Total debt balances, Current	0	657
Long-Term
Debt balance	264,301	255,099
Capital lease obligation	0	0
Small land purchase	$ 0	$ 0
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	(67,989)	(76,754)
Deferred debt issue costs	(3,384)	(3,821)
Debt balance	$ 263,777	$ 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