Goodwill & Acquired Intangible Assets (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill [Roll Forward]
Balance, beginning of period	$ 232,932,000	$ 53,011,000
Goodwill acquired during the period	109,385,000	179,910,000
Adjustments for prior year acquisitions	5,302,000
Foreign currency translation	6,700,000	11,000
Balance, end of period	354,319,000	232,932,000	53,011,000
Intangible Assets [Abstract]
Gross Carrying Amount	122,331,000	79,076,000
Accumulated Amortization	17,870,000	5,663,000
Net Carrying Amount	104,461,000	73,413,000
Weighted Average Amortization Period (years)	7.6	7.4
Amortization expense of intangible assets	14,800,000	2,700,000	1,700,000
Future amortization expense of intangible assets [Abstract]
For the year ended December 31, 2013	15,473,000
For the year ended December 31, 2014	14,808,000
For the year ended December 31, 2015	14,742,000
For the year ended December 31, 2016	14,645,000
For the year ended December 31, 2017	14,276,000
Thereafter	30,517,000
Non-compete agreements and trademarks [Member]
Intangible Assets [Abstract]
Gross Carrying Amount	10,281,000	6,258,000
Accumulated Amortization	2,082,000	1,091,000
Net Carrying Amount	8,199,000	5,167,000
Weighted Average Amortization Period (years)	5.7	5.1
Customer relationships and contracts [Member]
Intangible Assets [Abstract]
Gross Carrying Amount	112,050,000	72,818,000
Accumulated Amortization	15,788,000	4,572,000
Net Carrying Amount	96,262,000	68,246,000
Weighted Average Amortization Period (years)	9.4	9.6
Oilfield [Member]
Goodwill [Roll Forward]
Balance, beginning of period	225,770,000	45,862,000
Goodwill acquired during the period	109,385,000	179,910,000
Adjustments for prior year acquisitions	5,302,000
Foreign currency translation	6,742,000	(2,000)
Balance, end of period	347,199,000	225,770,000
Power Transmission [Member]
Goodwill [Roll Forward]
Balance, beginning of period	7,162,000	7,149,000
Goodwill acquired during the period	0	0
Adjustments for prior year acquisitions	0
Foreign currency translation	(42,000)	13,000
Balance, end of period	$ 7,120,000	$ 7,162,000