Changes in Operations Australia Arrium (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended			48 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Allowance for Doubtful Accounts Receivable, Write-offs		$ 6,317	$ 13,798	$ 7,125
Australian Operations [Member]
Asset Impairment Charges		$ 5,900	13,000
Arrium Limited [Member]
Amount invested in capital project					$ 78,000
Proceeds from Customers	$ 900
Arrium Limited [Member] | Australian Operations [Member]
Allowance for Doubtful Accounts Receivable, Write-offs			$ 8,100