Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Segment Data [Abstract]
Number of operating business segments	2		2
Segment Reporting Information [Line Items]
Net sales	$ 226,760	$ 152,847	$ 421,156	$ 279,969
Operating income	29,017	17,027	48,470	26,322
Other income (expense), net	(188)	(461)	(265)	(386)
Earnings from continuing operations before income tax provision and discontinued operations	28,829	16,566	48,205	25,936
Oil Field [Member]
Segment Reporting Information [Line Items]
Gross sales	180,736	114,896	335,919	205,097
Inter-segment sales	(1,814)	(632)	(3,275)	(913)
Net sales	178,922	114,264	332,644	204,184
Operating income	24,931	15,431	42,125	22,461
Other income (expense), net	(177)	(516)	(137)	(402)
Earnings from continuing operations before income tax provision and discontinued operations	24,754	14,915	41,988	22,059
Power Transmission [Member]
Segment Reporting Information [Line Items]
Gross sales	51,051	39,549	93,669	77,417
Inter-segment sales	(3,213)	(966)	(5,157)	(1,632)
Net sales	47,838	38,583	88,512	75,785
Operating income	4,086	1,596	6,345	3,861
Other income (expense), net	33	20	22	54
Earnings from continuing operations before income tax provision and discontinued operations	4,119	1,616	6,367	3,915
Corporate & Other [Member]
Segment Reporting Information [Line Items]
Gross sales	0	0	0	0
Inter-segment sales	0	0	0	0
Net sales	0	0	0	0
Operating income	0	0	0	0
Other income (expense), net	(44)	35	(150)	(38)
Earnings from continuing operations before income tax provision and discontinued operations	$ (44)	$ 35	$ (150)	$ (38)