NOTES PAYABLE TO BANKS - Interest incurred on credit facility, interest capitalized related to facilities and equipment under construction, and related weighted average interest rates (Details) - Revolving credit facility - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Line of Credit Facility [Line Items]
Interest incurred	$ 518	$ 472	$ 1,363	$ 886
Capitalized interest	$ 131	$ 115	$ 310	$ 212
Weighted average interest rate	2.32%	2.67%	1.80%	2.97%