ACQUISITIONS - Narrative (Details) - USD ($)				12 Months Ended
	Mar. 02, 2020	May 22, 2019	Feb. 28, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Total purchase consideration net of cash acquired				$ 223,230,000	$ 59,200,000	$ 5,315,000
Goodwill recorded in acquisition				$ 177,264,000	$ 33,663,000
Prime Distribution
Business Acquisition [Line Items]
Cash consideration for acquisition	$ 222,700,000
Goodwill recorded in acquisition	$ 176,500,000
Dema Service
Business Acquisition [Line Items]
Total purchase consideration net of cash acquired		$ 14,200,000
Goodwill recorded in acquisition		7,800,000
Goodwill recognized for foreign tax purposes		$ 0
Space Cargo
Business Acquisition [Line Items]
Total purchase consideration net of cash acquired			$ 45,500,000
Goodwill recorded in acquisition			26,700,000
Goodwill recognized for foreign tax purposes			$ 0