SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2015
Office furniture, equipment and light vehicles | Minimum
Property and Equipment
Estimated economic life	3 years
Office furniture, equipment and light vehicles | Maximum
Property and Equipment
Estimated economic life	5 years
Trailers, heavy vehicles and other site equipment | Minimum
Property and Equipment
Estimated economic life	5 years
Trailers, heavy vehicles and other site equipment | Maximum
Property and Equipment
Estimated economic life	15 years
Building
Property and Equipment
Estimated economic life	20 years
Leasehold Improvements
Property and Equipment
Estimated economic life	10 years