Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Sales by segment [Abstract]
Gross sales	$ 308,553	$ 231,787	$ 596,777	$ 429,588
Inter-segment sales	(2,909)	(5,027)	(11,597)	(8,432)
Net sales	305,644	226,760	585,180	421,156
Earnings (loss) before income taxes [Abstract]
Operating income (loss)	33,855	29,017	57,849	48,470
Other (expense) income, net	(3,404)	(188)	(7,172)	(265)
Earnings (loss) before income tax provision	30,451	28,829	50,677	48,205
Oil Field [Member]
Sales by segment [Abstract]
Gross sales	254,312	180,736	494,600	335,919
Inter-segment sales	(1,008)	(1,814)	(5,290)	(3,275)
Net sales	253,304	178,922	489,310	332,644
Earnings (loss) before income taxes [Abstract]
Operating income (loss)	31,731	24,931	54,204	42,125
Other (expense) income, net	(3,148)	(177)	(6,325)	(137)
Earnings (loss) before income tax provision	28,583	24,754	47,879	41,988
Power Transmission [Member]
Sales by segment [Abstract]
Gross sales	54,241	51,051	102,177	93,669
Inter-segment sales	(1,901)	(3,213)	(6,307)	(5,157)
Net sales	52,340	47,838	95,870	88,512
Earnings (loss) before income taxes [Abstract]
Operating income (loss)	2,124	4,086	3,645	6,345
Other (expense) income, net	53	33	38	22
Earnings (loss) before income tax provision	2,177	4,119	3,683	6,367
Corporate & Other [Member]
Sales by segment [Abstract]
Gross sales	0	0	0	0
Inter-segment sales	0	0	0	0
Net sales	0	0	0	0
Earnings (loss) before income taxes [Abstract]
Operating income (loss)	0	0	0	0
Other (expense) income, net	(309)	(44)	(885)	(150)
Earnings (loss) before income tax provision	$ (309)	$ (44)	$ (885)	$ (150)