QUARTERLY FINANCIAL DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly financial data (unaudited)
Net Sales	$ 736,307		$ 730,783		$ 777,008		$ 759,174		$ 743,827		$ 737,099		$ 790,052		$ 757,696		$ 3,003,272	$ 3,028,674	$ 2,624,431
Acquisition Transaction and Integration Costs					1,014		790		833		970		788		1,907		1,804	4,498	15,002
Business Combination, Bargain Purchase, Gain Recognized, Amount																	0	0	49,650
Gross profit	240,934		238,351		269,881		258,421		250,299		251,552		270,116		256,554		1,007,587	1,028,521	875,107
Income before income taxes	80,294	[1]	91,797	[2]	103,484	[3]	92,918	[4]	94,455	[1]	95,744	[2]	94,263	[3]	84,198	[4]	368,493	368,660	366,236
Net income	$ 63,716	[1]	$ 72,461	[2]	$ 85,452	[3]	$ 71,480	[4]	$ 86,839	[1]	$ 70,539	[2]	$ 68,864	[3]	$ 60,824	[4]	$ 293,109	$ 287,066	$ 247,503
Basic earnings per share (in dollars per share)	$ 1.04	[5]	$ 1.18	[5]	$ 1.37	[5]	$ 1.13	[5]	$ 1.36	[5]	$ 1.09	[5]	$ 1.05	[5]	$ 0.93	[5]	$ 4.73	$ 4.42	$ 3.76
Diluted earnings per share (in dollars per share)	$ 1.03	[5]	$ 1.17	[5]	$ 1.36	[5]	$ 1.12	[5]	$ 1.35	[5]	$ 1.07	[5]	$ 1.04	[5]	$ 0.92	[5]	$ 4.68	$ 4.37	$ 3.71
Rationalization and asset impairment net gains (charges)	$ (8,851)		$ (1,495)		$ (1,307)		$ (3,535)		$ (932)		$ (2,636)		$ (11,542)		$ (10,175)		$ (15,188)	$ (25,285)	$ (6,590)
Rationalization and asset impairment net gains (charges), after-tax	$ (7,284)		(1,240)		(937)		(2,814)		841		(2,575)		(10,362)		(7,870)
Resolution and settlements to uncertain tax positions					4,852
Income Tax Expense Benefit Net Resulting from Tax Reform Act									(4,424)		2,323				2,500		0	399	28,616
Acquisition Transaction and Integration Costs Net of Tax					867		$ 698		690		797		$ 675		1,520
Gain (Loss) on Disposition of Assets					3,554
GainLossOnDispositionofAssets1NetofTax					2,586
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment									(1,696)		(4,232)				(758)
Defined Benefit Plan Recognized Net Gain (Loss) Due To Settlements Net Of Tax									$ (1,272)		$ (3,176)				$ (569)
Business Combination, Inventory Step Up			1,609		1,399														4,578
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net																	7,601	0	0
Business Combination, Inventory Step Up Net of Tax					$ 1,049
International Welding [Member]
Quarterly financial data (unaudited)
Net Sales																	854,376	919,771	724,024
Rationalization and asset impairment net gains (charges)																	(11,702)	(25,285)	(5,498)
Gain (Loss) on Disposition of Assets																	3,554
Business Combination, Inventory Step Up																	1,609		4,578
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain (Loss), Net			$ 7,601														7,601
Americas Welding [Member]
Quarterly financial data (unaudited)
Net Sales																	1,815,746	1,806,514	1,609,779
Rationalization and asset impairment net gains (charges)																	(1,716)
Goodwill, Impairment Loss																			1,091
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment																		$ (6,686)	$ (8,150)
Business Combination, Inventory Step Up																	$ 1,399

[1] 2019 includes special item charges of $8,851 ($7,284 after-tax) for Rationalization and asset impairment charges. 2018 includes special item charges of $1,696 ($1,272 after-tax) for pension settlement charges, $932 ($841 gain after-tax) for Rationalization and asset impairment charges and gains or losses on the disposal of assets, a $4,424 credit related to the U.S. Tax Act and acquisition-related items including $833 ($690 after-tax) for acquisition transaction and integration costs.

[2] 2019 includes special item charges of $1,495 ($1,240 after-tax) for Rationalization and asset impairment charges, $1,609 for amortization of step up in value of acquired inventories and $7,601 for a gain on change in control related to the acquisition of Askaynak. 2018 includes special item charges of $4,232 ($3,176 after-tax) for pension settlement charges, $2,636 ($2,575 after-tax) for Rationalization and asset impairment charges, an adjustment to taxes on unremitted foreign earnings related to the U.S. Tax Act of $2,323 and acquisition-related items including $970 ($797 after-tax) for acquisition transaction and integration costs.

[3] 2019 includes special item charges of $3,554 ($2,586 after-tax) for gains on the disposal of assets, $1,399 ($1,049 after-tax) for amortization of step up in value of acquired inventories, $1,014 ($867 after-tax) for acquisition transaction and integration costs, $1,307 ($937 after-tax) for Rationalization and asset impairment charges and $4,852 for the settlement of a tax item as well as tax deductions associated with an investment in a subsidiary. 2018 includes special item charges of $11,542 ($10,362 after-tax) for Rationalization and asset impairment charges and $788 ($675 after-tax) for acquisition transaction and integration costs.

[4] 2019 includes special item charges of $3,535 ($2,814 after-tax) for Rationalization and asset impairment charges and $790 ($698 after-tax) for acquisition transaction and integration costs. 2018 includes special item charges of $758 ($569 after-tax) for pension settlement charges, $10,175 ($7,870 after-tax) for Rationalization and asset impairment charges, an adjustment to taxes on unremitted foreign earnings related to the U.S. Tax Act of $2,500 and $1,907 ($1,520 after-tax) for acquisition transaction and integration costs.

[5] The quarterly earnings per share ("EPS") amounts are each calculated independently. Therefore, the sum of the quarterly EPS amounts may not equal the annual totals.