RESTRUCTURING ACTIVITIES - Restructuring Activities - Restruciting Expenses and Related Costs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 4,400
ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	3,628
Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	772
Cost of Sales
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2,340
Cost of Sales | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,568
Cost of Sales | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	772
Selling, General and Administrative Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2,060
Selling, General and Administrative Expenses | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	2,060
Selling, General and Administrative Expenses | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0
Severance | Cost of Sales
Restructuring Cost and Reserve [Line Items]
Restructuring charges	423
Severance | Cost of Sales | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	423
Severance | Cost of Sales | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0
Severance | Selling, General and Administrative Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,978
Severance | Selling, General and Administrative Expenses | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,978
Severance | Selling, General and Administrative Expenses | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0
Other cash restructuring expenses | Cost of Sales
Restructuring Cost and Reserve [Line Items]
Restructuring charges	772
Other cash restructuring expenses | Cost of Sales | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0
Other cash restructuring expenses | Cost of Sales | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	772
Other cash restructuring expenses | Selling, General and Administrative Expenses
Restructuring Cost and Reserve [Line Items]
Restructuring charges	82
Other cash restructuring expenses | Selling, General and Administrative Expenses | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	82
Other cash restructuring expenses | Selling, General and Administrative Expenses | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	0
Asset impairments/net loss on disposals | Cost of Sales
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,145
Asset impairments/net loss on disposals | Cost of Sales | ESS
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,145
Asset impairments/net loss on disposals | Cost of Sales | Utility
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 0