LONG-TERM DEBT - Interest Expense (Details) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 11, 2015
Long-term debt
Interest expense	$ 1,700,000	$ 1,700,000
Interest paid	2,600,000	2,500,000
Interest capitalized	0	0
Amortization of loan costs	113,288	102,451
Debt discount	3,827,849
Amortization of discount	291,570	273,545
Interest expense
Long-term debt
Amortization of loan costs	113,000	102,000
4.50% Convertible Senior Notes due 2020
Long-term debt
Debt discount	3,800,000		$ 6,100,000
Amortization of discount		$ 273,000
4.50% Convertible Senior Notes due 2020 | Interest expense
Long-term debt
Amortization of discount	$ 292,000