LONG-TERM DEBT - Interest Expense (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Mar. 11, 2015
Long-term debt
Interest expense	$ 1,700,000	$ 1,800,000	$ 3,400,000	$ 3,500,000
Interest Paid	887,000	801,000	3,400,000	3,500,000
Interest capitalized	0	0	0	0
Amortization of loan costs			224,987	227,293
Debt discount	3,531,591		3,531,591
Amortization of discount			587,828	551,489
4.50% Convertible Senior Notes due 2020
Long-term debt
Debt discount	3,500,000		3,500,000		$ 6,100,000
Interest expense
Long-term debt
Amortization of loan costs	112,000	125,000	225,000	227,000
Interest expense | 4.50% Convertible Senior Notes due 2020
Long-term debt
Amortization of discount	$ 296,000	$ 278,000	$ 588,000	$ 551,000