ACQUISITIONS - Narrative (Details) - USD ($) $ in Thousands				12 Months Ended
	May 22, 2019	Feb. 28, 2019	Aug. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 28, 2020
Business Acquisition [Line Items]
Purchase consideration, net of cash acquired				$ 59,200	$ 5,315	$ 49,068
Goodwill recorded in acquisition				$ 33,663
Dema Service
Business Acquisition [Line Items]
Purchase consideration, net of cash acquired	$ 14,200
Goodwill recorded in acquisition	$ 7,800
Space Cargo
Business Acquisition [Line Items]
Purchase consideration, net of cash acquired		$ 45,000
Goodwill recorded in acquisition		$ 25,900
Milgram
Business Acquisition [Line Items]
Purchase consideration, net of cash acquired			$ 47,300
Goodwill recorded in acquisition			$ 28,300
Prime Distribution Services | Subsequent Event
Business Acquisition [Line Items]
Cash consideration per definitive agreement							$ 225,000