Long-Term Debt (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016	Feb. 17, 2007
Debt Instrument [Line Items]
Long-term debt	$ 149,486,000	$ 161,349,000
Less current maturities of long-term debt	(2,198,000)	(15,261,000)
Long-term debt net of current maturities	147,288,000	146,088,000
Convertible Subordinated Debt | Convertible Senior Notes at 5.00% February 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	150,000,000	150,000,000
Long-term debt	116,896,000	115,159,000
Debt Instrument, Unamortized Discount	(28,481,000)	(29,919,000)
Debt Instrument, Fee Amount	(4,623,000)	(4,922,000)
Debt Instrument, Net Carrying Amount	116,896,000	115,159,000
Convertible Subordinated Debt | Convertible Senior Subordinated Debentures at 4.125% February 2027
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 135,000,000
Long-term debt	0	13,039,000
Debt Instrument, Unamortized Discount		(311,000)
Notes Payable, Other Payables [Member]
Debt Instrument [Line Items]
Long-term debt	$ 32,590,000	$ 33,151,000