Segment Reporting (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Revenues	$ 198,349	$ 153,604	$ 566,893	$ 512,147
Gross Profit	25,150	18,919	69,354	68,955
Depreciation and Amortization Expense	3,628	4,163	11,431	12,571
Selling, General & Administrative Expenses	14,136	14,126	45,557	46,502
Operating Income	10,682	4,466	22,807	21,475
Capital and Other Expenditures [Abstract]
Capital Expenditures	2,768	2,546	10,611	7,787
Other Items	388	1,520	4,716	2,904
Operating Segments
Segment Reporting Information [Line Items]
Revenues	198,349	153,604	566,893	512,147
Corporate/ Other
Segment Reporting Information [Line Items]
Revenues	(3,257)	(1,807)	(8,399)	(6,188)
Gross Profit	(346)	(371)	(1,033)	(1,164)
Depreciation and Amortization Expense	673	484	2,051	1,812
Selling, General & Administrative Expenses	4,442	4,209	16,250	15,177
Operating Income	(4,789)	(4,579)	(17,283)	(16,341)
Capital and Other Expenditures [Abstract]
Capital Expenditures	476	290	1,795	867
Other Items	0	0	2,377	688
Global Truck & Bus
Segment Reporting Information [Line Items]
Revenues	122,049	96,036	344,048	324,666
Global Truck & Bus | Operating Segments
Segment Reporting Information [Line Items]
Revenues	121,497	95,728	342,964	323,895
Gross Profit	17,180	10,765	48,288	43,019
Depreciation and Amortization Expense	1,838	2,215	5,850	6,438
Selling, General & Administrative Expenses	5,534	5,329	16,688	17,466
Operating Income	11,350	5,144	30,716	24,679
Capital and Other Expenditures [Abstract]
Capital Expenditures	1,097	1,592	5,145	4,039
Other Items	373	1,329	1,341	1,704
Global Truck & Bus | Intersegment Revenues
Segment Reporting Information [Line Items]
Revenues	552	308	1,084	771
Global Construction & Agriculture
Segment Reporting Information [Line Items]
Revenues	79,557	59,375	231,244	193,669
Global Construction & Agriculture | Operating Segments
Segment Reporting Information [Line Items]
Revenues	76,852	57,876	223,929	188,252
Gross Profit	8,316	8,525	22,099	27,100
Depreciation and Amortization Expense	1,117	1,464	3,530	4,321
Selling, General & Administrative Expenses	4,160	4,588	12,619	13,859
Operating Income	4,121	3,901	9,374	13,137
Capital and Other Expenditures [Abstract]
Capital Expenditures	1,195	664	3,671	2,881
Other Items	15	191	998	512
Global Construction & Agriculture | Intersegment Revenues
Segment Reporting Information [Line Items]
Revenues	$ 2,705	$ 1,499	$ 7,315	$ 5,417