Commitments and Contingencies Metaldyne Corporation (Details) (USD $)	3 Months Ended
	Mar. 31, 2007	Dec. 31, 2012
Loss Contingencies [Line Items]
Common Stock Dividends, Shares	4,825,587
Loss Contingency, Estimate of Possible Loss		$ 6,000,000
Loss Contingency, Range of Possible Loss, Maximum		8,400,000
Loss Contingency, Range of Possible Loss, Portion Not Accrued		2,400,000
Allocated Share of Liabilities Not Readily Associated with the Business - TriMas		42.01%
Allocated Share of Liabilities Not Readily Associated with the Business - Metaldyne		57.99%
Indemnification Deductible		$ 50,000