SIGNIFICANT ACQUISITIONS - Estimated Fair Value of Assets Acquired and Liabilities Assumed (Details) € in Thousands, $ in Thousands	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 13, 2019 USD ($)	May 27, 2019 USD ($)	May 27, 2019 EUR (€)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract]
Goodwill	$ 522,929	$ 523,998
Zumbro River Brand, Inc.
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Cash and cash equivalents			$ 686
Accounts receivable			3,314
Inventories			4,052
Prepaid & other current assets			521
Property, plant and equipment			15,245
Other non-current assets			10
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract]
Accounts payable & accrued expenses			(1,651)
Debt			(5,345)
Deferred income taxes			(3,391)
Goodwill			18,156
Amount paid to shareholders			46,497
Debt paid on purchase date			5,345
Total amount paid on acquisition date			51,842
Zumbro River Brand, Inc. | Customer relationships
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Intangible assets			8,200
Zumbro River Brand, Inc. | Developed technology
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Intangible assets			4,400
Zumbro River Brand, Inc. | Trade name
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Intangible assets			$ 2,300
Chemogas
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Cash and cash equivalents				$ 4,412	€ 3,943
Accounts receivable				4,176
Inventories				957
Property, plant and equipment				15,972
Other non-current assets				1,491
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities [Abstract]
Accounts payable & accrued expenses				(3,261)
Debt				(12,222)
Other liabilities				(1,030)
Pension obligations (net)				(594)
Deferred income taxes				(12,856)
Goodwill				59,319
Amount paid to shareholders				99,102
Debt paid on purchase date				12,222	€ 10,924
Total amount paid on acquisition date				111,324
Chemogas | Customer relationships
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Intangible assets				39,158
Chemogas | Developed technology
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Intangible assets				2,461
Chemogas | Trade name
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets [Abstract]
Intangible assets				$ 1,119