v3.7.0.1
Business Combination Assets Acquired and Liabilities Assumed (Detail) - USD ($)
$ in Millions
 12 Months Ended
Jun. 02, 2014
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Business Acquisition [Line Items]          
Fair value of consideration $ 829.7        
Assets acquired:          
Receivables 120.2        
Inventories 40.1        
Prepaid expenses and other current assets 11.4        
Property and equipment 208.5        
Amortizable intangible assets 369.1        
Other assets 9.1        
Total assets acquired 758.4        
Liabilities assumed:          
Accounts payable 94.7        
Accrued liabilities 25.7        
Deferred tax liabilities 47.5        
Short-term debt 1.7        
Other long-term liabilities 20.7        
Total liabilities assumed 190.3        
Net identifiable assets acquired, net of cash and cash equivalents 568.1        
Goodwill 261.6 $ 907.7 $ 907.7 $ 907.7 $ 657.9
Inventories 40.1        
Property and equipment 208.5        
Amortizable intangible assets 369.1        
Machinery and Equipment [Member] | Minimum          
Liabilities assumed:          
Property and equipment, estimated useful lives   1 year      
Machinery and Equipment [Member] | Maximum          
Liabilities assumed:          
Property and equipment, estimated useful lives   20 years      
ASP Grede Intermediate Holdings LLC [Member]          
Business Acquisition [Line Items]          
Fair value of consideration 829.7        
Assets acquired:          
Inventories 40.1        
Property and equipment 208.5        
Amortizable intangible assets 369.1        
Liabilities assumed:          
Inventories 40.1        
Property and equipment 208.5        
Amortizable intangible assets 369.1        
ASP Grede Intermediate Holdings LLC [Member] | Customer Relationships and Platforms [Member]          
Assets acquired:          
Amortizable intangible assets 338.7        
Liabilities assumed:          
Amortizable intangible assets $ 338.7        
Intangible assets, remaining useful life 10 years 10 years      
ASP Grede Intermediate Holdings LLC [Member] | Other: Trade Names [Member]          
Assets acquired:          
Amortizable intangible assets $ 30.4        
Liabilities assumed:          
Amortizable intangible assets $ 30.4        
Intangible assets, remaining useful life 15 years 15 years      
ASP Grede Intermediate Holdings LLC [Member] | Land [Member]          
Assets acquired:          
Property and equipment $ 12.2        
Liabilities assumed:          
Property and equipment 12.2        
ASP Grede Intermediate Holdings LLC [Member] | Building [Member]          
Assets acquired:          
Property and equipment 31.8        
Liabilities assumed:          
Property and equipment $ 31.8        
ASP Grede Intermediate Holdings LLC [Member] | Building [Member] | Minimum          
Liabilities assumed:          
Property and equipment, estimated useful lives 5 years        
ASP Grede Intermediate Holdings LLC [Member] | Building [Member] | Maximum          
Liabilities assumed:          
Property and equipment, estimated useful lives 29 years        
ASP Grede Intermediate Holdings LLC [Member] | Machinery and Equipment [Member]          
Assets acquired:          
Property and equipment $ 148.8        
Liabilities assumed:          
Property and equipment $ 148.8        
ASP Grede Intermediate Holdings LLC [Member] | Machinery and Equipment [Member] | Minimum          
Liabilities assumed:          
Property and equipment, estimated useful lives 1 year        
ASP Grede Intermediate Holdings LLC [Member] | Machinery and Equipment [Member] | Maximum          
Liabilities assumed:          
Property and equipment, estimated useful lives 20 years        
ASP Grede Intermediate Holdings LLC [Member] | Assets Not Yet Placed In Service [Member]          
Assets acquired:          
Property and equipment $ 15.7        
Liabilities assumed:          
Property and equipment 15.7        
Raw Materials [Member] | ASP Grede Intermediate Holdings LLC [Member]          
Assets acquired:          
Inventories 11.9        
Liabilities assumed:          
Inventories 11.9        
Work In Process [Member] | ASP Grede Intermediate Holdings LLC [Member]          
Assets acquired:          
Inventories 12.6        
Liabilities assumed:          
Inventories 12.6        
Finished Goods [Member] | ASP Grede Intermediate Holdings LLC [Member]          
Assets acquired:          
Inventories 15.6        
Liabilities assumed:          
Inventories $ 15.6