Segment Data (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Data [Abstract]
Number of operating business segments	2		2
Segment Reporting Information [Line Items]
Gross sales	$ 236,412	$ 173,414	$ 666,000	$ 455,928
Inter-segment sales	(4,698)	(1,276)	(13,130)	(3,821)
Net sales	231,714	172,138	652,870	452,107
Operating income	23,965	19,801	72,435	46,124
Other (expense) income, net	(150)	(64)	(415)	(451)
Earnings from continuing operations before income tax provision and discontinued operations	23,815	19,737	72,020	45,673
Oil Field [Member]
Segment Reporting Information [Line Items]
Gross sales	184,857	130,015	520,776	335,113
Inter-segment sales	(1,352)	(528)	(4,627)	(1,441)
Net sales	183,505	129,487	516,149	333,672
Operating income	21,011	17,826	63,136	40,288
Other (expense) income, net	(11)	88	(148)	(315)
Earnings from continuing operations before income tax provision and discontinued operations	21,000	17,914	62,988	39,973
Power Transmission [Member]
Segment Reporting Information [Line Items]
Gross sales	51,555	43,399	145,224	120,815
Inter-segment sales	(3,346)	(748)	(8,503)	(2,380)
Net sales	48,209	42,651	136,721	118,435
Operating income	2,954	2,975	9,299	6,836
Other (expense) income, net	21	(34)	43	20
Earnings from continuing operations before income tax provision and discontinued operations	2,975	2,941	9,342	6,856
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	(1,000)	0	(1,000)
Other (expense) income, net	(160)	(118)	(310)	(156)
Earnings from continuing operations before income tax provision and discontinued operations	$ (160)	$ (1,118)	$ (310)	$ (1,156)