ACQUISITIONS (Details) - USD ($) $ in Thousands		1 Months Ended		3 Months Ended								12 Months Ended
		Jul. 31, 2017		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquisitions
Business Combination, Inventory Step Up				$ 2,264	$ 2,314							$ 4,578
Acquisition Transaction and Integration Costs				3,616	3,273	$ 4,498	$ 3,615					15,002
Annual sales at the date of acquisition				747,185	669,491	$ 626,858	$ 580,897	$ 563,828	$ 567,646	$ 592,418	$ 550,772	2,624,431	$ 2,274,614	$ 2,535,791
Business Combination, Bargain Purchase, Gain Recognized, Amount				(1,935)	$ 51,585							49,650	0	0
Payments to Acquire Businesses, Net of Cash Acquired												72,468	71,567	$ 37,076
Business Combination Receivable From Seller				$ 10,670								10,670
Air Liquide Welding [Member]
Acquisitions
Business Combination, Agreed Upon Purchase Price		$ 135,123
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Receivables		89,442
Annual sales at the date of acquisition												182,000	$ 400,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Inventory	[1]	97,803
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	[2]	73,056
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	[3]	11,715
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Accounts Payable		(65,640)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Pension Liability		(67,563)
Business Combination, Bargain Purchase, Gain Recognized, Amount		49,650
Business Combination, Recognized Identifiable Other Assets Acquired and Other Liabilities Assumed, Net	[4]	(27,210)
Payments to Acquire Businesses, Net of Cash Acquired		$ 61,953	[5]									61,953
Indefinite-lived Intangible Assets Acquired												7,099
Other Intangible Assets | Air Liquide Welding [Member]
Acquisitions
Finite-lived Intangible Assets Acquired												3,433
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		9 years
Trademarks and trade names | Air Liquide Welding [Member]
Acquisitions
Finite-lived Intangible Assets Acquired												$ 1,183
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		10 years

[1] Inventories acquired were sold in 2017 resulting in a $4,578 increase in cost of sales for the amortization of step up in the value of acquired inventories.

[2] Property, plant and equipment acquired includes a number of manufacturing and distribution sites, including the related facilities, land and leased sites, and machinery and equipment for use in manufacturing operations.

[3] $7,099 of the intangible asset balance was assigned to a trade name expected to have an indefinite life. Of the remaining amount, $1,183 was assigned to a finite-lived trade name (10 year weighted average useful life) and $3,433 was assigned to other intangible assets (9 year weighted average life).

[4] Consists primarily of other accrued liabilities.

[5] Reflects a receivable from seller of $10,670 as of December 31, 2017 for an agreed upon purchase price adjustment received in the first quarter of 2018.