Presentation, Summary of Significant Accounting Policies and Recent Accounting Standard Updates - Additional Information (Detail) $ / shares in Units, shares in Millions		1 Months Ended	3 Months Ended			12 Months Ended
	Jun. 11, 2010 USD ($) $ / shares shares	Jun. 30, 2010 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) entity $ / shares	Sep. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) entity item customer $ / shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Feb. 28, 2015 $ / shares	Dec. 31, 2014 USD ($)
Schedule Of Significant Accounting Policies
Inventories			$ 107,300,000		$ 118,200,000	$ 107,300,000	$ 118,200,000
Identifiable intangible assets, net					12,500,000		12,500,000
Number of VIE treated as unconsolidated equity method investment | entity			1			1
Equity method investment			$ 7,900,000		5,000,000	$ 7,900,000	5,000,000
Accumulated other comprehensive loss on foreign currency			9,700,000		11,200,000	9,700,000	11,200,000	$ 7,200,000
Currency translation gains (losses)						0	0	300,000
Gain (loss) related to impact of foreign exchange rates on intercompany loans						2,400,000	(2,400,000)	(1,300,000)
Impairment on property, plant and equipment			40,500,000			$ 40,500,000
Percentage of weight given to DCF method for goodwill impairment test						50.00%
Percentage of weight given to GPC method for goodwill impairment test						50.00%
Fair value inputs, long-term revenue growth rate						3.00%
Goodwill impairment				$ 33,600,000	61,800,000	$ 33,600,000	61,800,000	0
Impairment on intangible assets			$ 10,100,000			$ 10,100,000	100,000	0
Warrant issued to purchase common stock | shares	1.5	1.5
Aggregate purchase price of common stock warrant	$ 300,000	$ 300,000
Term of warrants		10 years
Exercise price of warrants | $ / shares	$ 10.30	$ 10.30	$ 5.64			$ 5.64			$ 5.64
Deferred tax valuation allowance			$ 256,100,000		406,000,000	$ 256,100,000	406,000,000	$ 382,400,000		$ 385,600,000
Number of landfills to be capped | item						3
Repurchase reserve			0		$ 0	$ 0	0
Cosmedicine
Schedule Of Significant Accounting Policies
Inventories			0			0
Identifiable intangible assets, net			0			$ 0
Impairment on intangible assets							100,000
RANA
Schedule Of Significant Accounting Policies
Fair value inputs weighted average capital cost rate						9.70%
Goodwill impairment						$ 33,600,000	61,800,000
Impairment on intangible assets						$ 10,100,000
RAEU
Schedule Of Significant Accounting Policies
Fair value inputs weighted average capital cost rate						10.40%
Maximum
Schedule Of Significant Accounting Policies
Period over which major repair and maintenance projects are expensed						24 months
Equity Method Investments
Schedule Of Significant Accounting Policies
Impairment loss						$ 0	$ 0
Equity Method Investments | Beck Trading
Schedule Of Significant Accounting Policies
Equity method investment			7,900,000			7,900,000
Maximum loss exposure amount			$ 11,000,000			$ 11,000,000
Customer Concentration Risk | Consolidated Revenue
Schedule Of Significant Accounting Policies
Number of customers exceeding the concentration risk threshold percentage | customer						0
Customer Concentration Risk | Consolidated Revenue | Nemak | RANA and RAEU
Schedule Of Significant Accounting Policies
Concentration Risk, Percentage							12.00%	14.00%
Customer Concentration Risk | Consolidated Revenue | Honda Motor | RANA
Schedule Of Significant Accounting Policies
Concentration Risk, Percentage							11.00%	10.00%
Customer Concentration Risk | Accounts Receivable | Customer Three
Schedule Of Significant Accounting Policies
Number of customers exceeding the concentration risk threshold percentage | customer						1
Customer Concentration Risk | Accounts Receivable | Customer Three | Minimum
Schedule Of Significant Accounting Policies
Concentration Risk, Percentage						10.00%
Customer Concentration Risk | Accounts Receivable | Customer Three | Maximum
Schedule Of Significant Accounting Policies
Concentration Risk, Percentage						20.00%
Customer Concentration Risk | Accounts Receivable | Top Ten Customers
Schedule Of Significant Accounting Policies
Concentration Risk, Percentage						55.60%
Supplier Concentration Risk | Metal Purchases
Schedule Of Significant Accounting Policies
Number of suppliers exceeding the concentration risk threshold percentage | item						0
Supplier Concentration Risk | Metal Purchases | Top Ten Suppliers
Schedule Of Significant Accounting Policies
Concentration Risk, Percentage						16.90%
Selling, General and Administrative Expenses
Schedule Of Significant Accounting Policies
Advertising costs						$ 100,000	$ 400,000	$ 300,000