GRT Acquisition - Estimated Fair Values of Assets Acquired and Liabilities Assumed (Details) - USD ($)	13 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 01, 2016	Dec. 31, 2010
Assets
Goodwill	$ 54,613,000	$ 52,705,000		$ 0
GRT Acquisition
Assets
Cash	8,091,000		$ 8,091,000
Accounts receivable	2,844,000		2,844,000
Notes receivable	3,050,000		3,050,000
Inventory	8,468,000		7,983,000
Other current assets	981,000		981,000
Property, plant & equipment	47,541,000		46,712,000
Intangible assets	7,428,000		7,412,000
Other long-term assets	289,000		289,000
Goodwill	33,250,000		33,861,000
Liabilities
Accounts payable	(62,289,000)		(61,570,000)
Notes payable	(10,122,000)		(10,122,000)
Accrued liabilities	(2,866,000)		(2,866,000)
Long-term debt	(3,383,000)		(3,383,000)
Other long-term liabilities	(940,000)		(940,000)
Net assets and liabilities assumed	32,342,000		32,342,000
Noncontrolling shareholder interest	(18,323,000)		(18,323,000)
Cooper Tire & Rubber Company consideration	14,019,000		$ 14,019,000
Adjustments
Inventory	485,000
Property, plant & equipment	829,000
Intangible assets	16,000
Goodwill	(611,000)
Accounts payable	$ (719,000)