SEGMENT INFORMATION (Financial Information of Reportable Segments) (Details) - USD ($) $ in Thousands		3 Months Ended																12 Months Ended
		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financial information for the reportable segments
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment		$ (1,696)		$ (4,232)				$ (758)		$ (2,867)		$ (5,283)
Goodwill, Impairment Loss	[1]																		$ 1,091
Loss on deconsolidation of Venezuelan subsidiary																		$ 0	0	$ 34,348
Net sales		743,827		737,099		$ 790,052		757,696		747,185		669,491		$ 626,858		$ 580,897		3,028,674	2,624,431	2,274,614
Revenue from Related Parties																		0	0	0
Segment, including Inter-segment, sales																		3,028,674	2,624,431	2,274,614
EBIT, as adjusted																		422,694	370,338	328,723
Special items charge (Gain)																		36,469	(15,330)	34,348
EBIT																		386,225	385,668	294,375
Interest income																		6,938	4,788	2,092
Interest expense																		(24,503)	(24,220)	(19,079)
Income before income taxes		94,455	[2]	95,744	[3]	94,263	[4]	84,198	[5]	73,728	[2]	130,642	[3]	83,966	[4]	77,900	[5]	368,660	366,236	277,388
Total assets		2,349,825								2,406,547								2,349,825	2,406,547	1,943,437
Equity investments in affiliates		31,228								28,526								31,228	28,526	27,301
Capital expenditures																		71,246	61,656	49,877
Depreciation and amortization																		72,346	68,115	65,073
Rationalization and asset impairment charges (gains)		932		2,636		11,542		10,175		6,590								25,285	6,590	0
Business Combination, Inventory Step Up										2,264		2,314							4,578
Acquisition Transaction and Integration Costs		833		$ 970		$ 788		$ 1,907		3,616		3,273		$ 4,498		$ 3,615		4,498	15,002
Business Combination, Bargain Purchase, Gain Recognized, Amount										(1,935)		$ 51,585						0	49,650	0
The Harris Products Group
Financial information for the reportable segments
Goodwill, Impairment Loss	[1]																		0
Net sales																		302,389	290,628	272,343
Revenue from Related Parties																		6,969	8,190	8,709
Segment, including Inter-segment, sales																		309,358	298,818	281,052
EBIT, as adjusted																		36,564	36,442	32,380
Special items charge (Gain)																		0	0	0
EBIT																		36,564	36,442	32,380
Total assets		203,095								175,151								203,095	175,151	161,391
Equity investments in affiliates		0								0								0	0	0
Capital expenditures																		2,909	3,949	2,209
Depreciation and amortization																		3,045	2,885	2,860
Corporate / Eliminations
Financial information for the reportable segments
Loss on deconsolidation of Venezuelan subsidiary																				34,348
Net sales																		0	0	0
Revenue from Related Parties																		(144,481)	(124,432)	(118,296)
Segment, including Inter-segment, sales																		(144,481)	(124,432)	(118,296)
EBIT, as adjusted																		(8,887)	309	564
Special items charge (Gain)	[6]																	4,498	(34,648)	34,348
EBIT																		(13,385)	34,957	(33,784)
Total assets		(99,307)								57,990								(99,307)	57,990	(25,594)
Equity investments in affiliates		0								0								0	0	0
Capital expenditures																		0	0	0
Depreciation and amortization																		(91)	(172)	(209)
Acquisition Transaction and Integration Costs																		4,498	15,002
Americas Welding [Member]
Financial information for the reportable segments
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement and Curtailment																		(6,686)	(8,150)
Goodwill, Impairment Loss	[1]																		1,091
Net sales																		1,806,514	1,609,779	1,494,982
Revenue from Related Parties																		118,936	97,382	93,612
Segment, including Inter-segment, sales																		1,925,450	1,707,161	1,588,594
EBIT, as adjusted																		340,744	291,866	266,633
Special items charge (Gain)	[7]																	6,686	9,242	0
EBIT																		334,058	282,624	266,633
Total assets		1,418,905								1,253,411								1,418,905	1,253,411	1,278,417
Equity investments in affiliates		4,204								4,037								4,204	4,037	3,946
Capital expenditures																		42,053	43,158	35,314
Depreciation and amortization																		47,008	47,038	47,359
International Welding [Member]
Financial information for the reportable segments
Goodwill, Impairment Loss	[1]																		0
Net sales																		919,771	724,024	507,289
Revenue from Related Parties																		18,576	18,860	15,975
Segment, including Inter-segment, sales																		938,347	742,884	523,264
EBIT, as adjusted																		54,273	41,721	29,146
Special items charge (Gain)	[8]																	25,285	10,076	0
EBIT																		28,988	31,645	29,146
Total assets		827,132								919,995								827,132	919,995	529,223
Equity investments in affiliates		$ 27,024								$ 24,489								27,024	24,489	23,355
Capital expenditures																		26,284	14,549	12,354
Depreciation and amortization																		22,384	18,364	$ 15,063
Rationalization and asset impairment charges (gains)																		$ 25,285	5,498
Business Combination, Inventory Step Up																			$ 4,578

[1] The Company performed an interim goodwill impairment test, using a combination of income and market valuation approaches, resulting in a non-cash impairment charge to the carrying value of goodwill. The impairment charge is recorded within Rationalization and asset impairment charges in the accompanying Consolidated Statements of Income.

[2] 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. 2017 includes special item charges of $2,867 ($1,770 after-tax) for pension settlement charges, $6,590 ($6,198 after-tax) for rationalization and asset impairment charges, $28,616 for the net impact of the U.S. Tax Act and acquisition-related items including $2,264 ($1,708 after-tax) in amortization of step up in value of acquired inventories, $3,616 ($3,102 after-tax) for acquisition transaction and integration costs and a $1,935 adjustment to the bargain purchase gain

[3] 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.2017 includes special item charges of $5,283 ($3,260 after-tax) for pension settlement charges and acquisition-related items including $2,314 ($1,745 after-tax) in amortization of step up in value of acquired inventories, $3,273 ($2,229 after-tax) for acquisition transaction and integration costs and a $51,585 bargain purchase gain

[4] 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.2017 includes special item charges of $4,498 ($3,494 after-tax) related to acquisition transaction and integration costs

[5] 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.2017 includes special item charges of $3,615 ($2,734 after-tax) related to acquisition transaction costs.

[6] 2018 special items reflect acquisition and acquisition transaction and integration costs of $4,498 related to the Air Liquide Welding acquisition as discussed in Note 4 to the consolidated financial statements.2017 special items reflect a bargain purchase gain of $49,650 and acquisition transaction and integration costs of $15,002 related to the Air Liquide Welding acquisition as discussed in Note 4 to the consolidated financial statements.2016 special items reflect a loss of $34,348 related to the deconsolidation of the Company's Venezuelan subsidiary.

[7] Special items in 2018 reflect pension settlement charges of $6,686 in Americas Welding related to lump sum pension payments. 2017 special items reflect pension settlement charges of $8,150 related to lump sum pension payments, as well as non-cash charges of $1,091 related to the impairment of goodwill.

[8] 2018 special items reflect charges of $25,285 related to employee severance, asset impairments, gains or losses on disposal of assets and other related costs.2017 special items reflect amortization of step up in value of acquired inventories of $4,578 related to the Air Liquide Welding acquisition as discussed in Note 4 to the consolidated financial statements, as well as charges of $5,498 related to employee severance, asset impairments and other related costs.