Information on Business Segments (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment	2
Revenues	$ 1,436,499	$ 1,230,754	$ 1,193,975
Operating profit	210,278	192,178	168,396
Assets	2,365,716	2,137,539	2,061,900
Depreciation and amortization	90,150	80,154	78,242
Capital expenditures	58,712	47,577	45,982
Interest expense	14,571	11,883	10,698
Other expense (income), net	8	(2,326)	(248)
Income before income taxes	$ 195,699	$ 182,621	$ 157,946
General Electric [Member]
Segment Reporting Information [Line Items]
Revenue by major customer	18.00%	17.00%	18.00%
Aerospace [Member]
Segment Reporting Information [Line Items]
Revenues	$ 462,600	$ 406,500	$ 411,700
Operating profit	83,200	62,500	65,400
Assets	667,100	647,800	654,100
Depreciation and amortization	33,600	30,000	30,800
Capital expenditures	27,500	21,100	17,200
Industrial [Member]
Segment Reporting Information [Line Items]
Revenues	973,900	824,200	782,300
Operating profit	127,100	129,700	103,000
Assets	1,505,400	1,356,100	1,241,200
Depreciation and amortization	54,800	49,500	46,000
Capital expenditures	31,000	25,900	28,700
Other [Member]
Segment Reporting Information [Line Items]
Revenues	0	0	0
Operating profit	0	0	0
Assets	193,300	133,700	166,500
Depreciation and amortization	1,700	700	1,300
Capital expenditures	$ 200	$ 500	$ 100