Discontinued Operations Discontinued Operations - Cequent Spin-off (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of Horizon Shares Received in Spin-off		2
TriMas Number of Common Shares Held		5
Cash distribution received from Cequent spin-off	$ 214,500	$ 214,500
Cequent businesses [Member] | Discontinued Operations, Disposed of by Means Other than Sale, Spinoff [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Group, Including Discontinued Operation, Cash and Cash Equivalents		17,050
Disposal Group, Including Discontinued Operation, Accounts, Notes and Loans Receivable, Net		92,750
Disposal Group, Including Discontinued Operation, Inventory, Current		125,750
Disposal Group, Including Discontinued Operation, Prepaid and Other Assets, Current		6,520
Disposal Group, Including Discontinued Operation, Assets, Current		242,070
Disposal Group, Including Discontinued Operation, Property, Plant and Equipment, Noncurrent		48,870
Disposal Group, Including Discontinued Operation, Goodwill, Noncurrent		5,630
Disposal Group, Including Discontinued Operation, Intangible Assets, Noncurrent		61,400
Disposal Group, Including Discontinued Operation, Other Assets, Noncurrent		16,390
Disposal Group, Including Discontinued Operation, Assets		374,360	$ 0
Disposal Group, Including Discontinued Operations, Debt, Current		17,940
Disposal Group, Including Discontinued Operation, Accounts Payable, Current		81,830
Disposal Group, Including Discontinued Operation, Accrued Liabilities, Current		44,190
Disposal Group, Including Discontinued Operation, Liabilities, Current		143,960
Disposal Group, Including Discontinued Operations, Debt, Noncurrent		195,460
Disposal Group, Including Discontinued Operation, Deferred Tax Liabilities, Noncurrent		4,860
Disposal Group, Including Discontinued Operation, Other Liabilities, Noncurrent		27,900
Disposal Group, Including Discontinued Operation, Liabilities		$ 372,180	$ 0