Discontinued Operations and Disposition - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended			9 Months Ended
	Sep. 30, 2019	May 31, 2019	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Impairment loss				$ 10,082
Proceeds from sale of the Avonmore Plant (Note 2)		$ 3,700				$ 3,700	$ 0
ASW Steel Inc [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Asset write down charge								$ 15,000
Proceeds from purchase agreement	$ 8,000
Purchase price, after estimated purchase price adjustments	$ 4,292		$ 4,292			4,292
Net sales			9,992		$ 14,849	35,045	51,227
ASW Steel Inc [Member] | Union Electric Steel Corporation [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Net sales			$ 360		$ 1,457	$ 4,381	$ 20,117