SIGNIFICANT ACCOUNTING POLICIES - Goodwill (Details) - USD ($)	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes to the carrying amount of goodwill
Goodwill balance	$ 16,097,000	$ 16,097,000	$ 16,097,000
Goodwill impairment			(17,584,000)	$ 0	$ (11,464,000)
Goodwill balance			0	16,097,000
NobelClad
Changes to the carrying amount of goodwill
Goodwill balance	16,097,000	16,097,000	16,097,000	17,190,000
Adjustment due to recognition of tax benefit of tax amortization of certain goodwill			(450,000)	(507,000)
Adjustment due to exchange rate differences			1,937,000	(586,000)
Goodwill impairment	$ 0	$ (17,584,000)	(17,584,000)
Goodwill balance			$ 0	$ 16,097,000	$ 17,190,000