Presentation, Summary of Significant Accounting Policies and Recent Accounting 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	Dec. 31, 2016 USD ($) Entity $ / shares	Dec. 31, 2016 USD ($) Entity $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Feb. 28, 2015 $ / shares	Dec. 31, 2013 USD ($)
Schedule Of Significant Accounting Policies [Line Items]
Number of VIE treated as unconsolidated equity method investment | Entity			1	1
Impairment loss				$ 800,000
Equity method investment			$ 5,000,000	5,000,000
Accumulated other comprehensive loss on foreign currency			11,200,000	11,200,000	$ 7,200,000
Currency translation gains (losses)				0	300,000	$ 0
Gain (loss) related to impact of foreign exchange rates on intercompany loans				(2,400,000)	(1,300,000)	0
Impairment on property, plant and equipment				$ 0
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			$ 61,800,000	$ 61,800,000	0	0
Warrant issued to purchase common stock | shares	1.5
Aggregate purchase price of common stock warrant	$ 300,000
Term of warrants		10 years
Exercise price of warrants | $ / shares	$ 10.30		$ 5.64	$ 5.64			$ 5.64
Deferred tax valuation allowance			$ 406,000,000	$ 406,000,000	382,400,000	385,600,000		$ 375,000,000
Deferred tax valuation allowance released amount based on expected future taxable income						$ 5,100,000
Repurchase reserve			0	0	700,000
U.S.
Schedule Of Significant Accounting Policies [Line Items]
Deferred tax valuation allowance			400,600,000	400,600,000	377,000,000
Foreign
Schedule Of Significant Accounting Policies [Line Items]
Deferred tax valuation allowance			5,400,000	5,400,000	5,400,000
Cosmedicine
Schedule Of Significant Accounting Policies [Line Items]
Impairment on intangible assets				100,000	$ 0
RAEU | 2016 Goodwill Impairment Test
Schedule Of Significant Accounting Policies [Line Items]
Estimated amount of fair value including goodwill in excess of carrying value			17,500,000	$ 17,500,000
Minimum | Income Approach Method
Schedule Of Significant Accounting Policies [Line Items]
Fair value inputs weighted average capital cost rate				10.00%
Maximum | Income Approach Method
Schedule Of Significant Accounting Policies [Line Items]
Fair value inputs weighted average capital cost rate				10.50%
Beck Aluminum International, LLC (“Beck Trading”)
Schedule Of Significant Accounting Policies [Line Items]
Equity method investment			5,000,000	$ 5,000,000
Maximum loss exposure amount			$ 11,800,000	11,800,000
Equity Method Investments
Schedule Of Significant Accounting Policies [Line Items]
Impairment loss				$ 0
Customer Concentration Risk | Consolidated Revenue
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage						0.00%
Customer Concentration Risk | Consolidated Revenue | Nemak
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				12.00%	14.00%
Customer Concentration Risk | Consolidated Revenue | Honda Motor
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				11.00%	10.00%
Customer Concentration Risk | Trade Accounts Receivable | Three Customer | Minimum
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				10.00%
Customer Concentration Risk | Trade Accounts Receivable | Three Customer | Maximum
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				20.00%
Customer Concentration Risk | Trade Accounts Receivable | Ten Customer
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				60.10%
Customer Concentration Risk | Metal Purchases
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				10.00%
Customer Concentration Risk | Metal Purchases | Ten Suppliers
Schedule Of Significant Accounting Policies [Line Items]
Concentration Risk, Percentage				25.00%
Selling, General and Administrative Expenses
Schedule Of Significant Accounting Policies [Line Items]
Advertising costs				$ 400,000	$ 300,000	$ 0