ACQUISITION - Estimated fair values of acquired assets and liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Purchase Allocation
Goodwill	$ 299,008		$ 300,337
Operating revenues	1,335,074	$ 829,213
Operating income (loss)	94,928	$ 32,191
MoLo Solutions, LLC
Purchase Allocation
Accounts receivable	134,702
Prepaid expenses	468
Property and equipment	2,309
Operating lease right-of use assets	844
Intangible assets	76,900
Other assets	170
Total identifiable assets acquired	215,393
Accounts payable	91,228
Accrued expenses and other current liabilities	2,724
Operating lease liabilities	983
Total liabilities	94,935
Total identifiable net assets	120,458
Goodwill	212,640
Net assets acquired	$ 333,098