REVENUE - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenues	$ 109,351	$ 90,184
Oil and gas
Disaggregation of Revenue [Line Items]
Revenues	49,576
Petrochemical
Disaggregation of Revenue [Line Items]
Revenues	19,778
Electric utility
Disaggregation of Revenue [Line Items]
Revenues	19,258
Traction power
Disaggregation of Revenue [Line Items]
Revenues	5,009
All others
Disaggregation of Revenue [Line Items]
Revenues	15,730
United States
Disaggregation of Revenue [Line Items]
Revenues	89,898
Canada
Disaggregation of Revenue [Line Items]
Revenues	9,715
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenues	5,441
Asia/Pacific
Disaggregation of Revenue [Line Items]
Revenues	3,744
Mexico, Central and South America
Disaggregation of Revenue [Line Items]
Revenues	$ 553