ACQUISITIONS (Details)									3 Months Ended								6 Months Ended	12 Months Ended			24 Months Ended	135 Months Ended
	Aug. 01, 2018 USD ($) shares	Jul. 01, 2018 USD ($) shares	Jun. 06, 2018 USD ($) $ / shares shares	Dec. 29, 2017 USD ($)	Dec. 01, 2017 USD ($) shares	Sep. 01, 2017 USD ($)	Jul. 01, 2017 USD ($) shares	May 01, 2017 USD ($) shares	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) shares	Dec. 31, 2019 USD ($) item
ACQUISITIONS
Number of shares transferred | shares																					0
Common stock issued in acquisitions													$ 19,700,000				$ 19,700,000		$ 19,700,000	$ 64,000,000
Revenue									$ 403,000,000	$ 450,400,000	$ 450,600,000	$ 433,000,000	447,000,000	$ 461,600,000	$ 376,900,000	$ 327,600,000		$ 1,737,000,000	1,613,100,000	846,300,000
Net income (loss)									(18,400,000)	$ (273,300,000)	$ (6,400,000)	(9,300,000)	(20,100,000)	$ 2,200,000	13,500,000	$ (800,000)		(307,400,000)	(5,200,000)	27,000,000
Allocation of the purchase price paid to the fair values of the net assets
Prepaid and other current assets									21,900,000				26,300,000				26,300,000	21,900,000	26,300,000		$ 21,900,000	$ 21,900,000
Property and equipment									761,400,000				832,400,000				832,400,000	761,400,000	832,400,000		761,400,000	761,400,000
Goodwill									139,900,000				258,400,000				258,400,000	139,900,000	258,400,000	302,700,000	139,900,000	139,900,000
Amortization of intangible assets																		14,300,000	16,700,000	6,700,000
Accumulated amortization									60,600,000				46,300,000				46,300,000	60,600,000	46,300,000		60,600,000	60,600,000
Business Acquisition, Pro Forma Information [Abstract]
Pro forma revenue																			1,747,400,000
Pro forma net income (loss)																			$ (5,700,000)
Pro forma net income (loss) per common share:
Basic | $ / shares																			$ (0.09)
Diluted | $ / shares																			$ (0.09)
Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Accumulated amortization									18,400,000				12,800,000				12,800,000	18,400,000	$ 12,800,000		18,400,000	18,400,000
Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Accumulated amortization									$ 42,200,000				33,500,000				33,500,000	$ 42,200,000	33,500,000		$ 42,200,000	$ 42,200,000
Minimum
ACQUISITIONS
Number of open-deck trucking companies acquired | item																						20
Acquisition 2017
ACQUISITIONS
Revenue																				154,000,000
Net income (loss)																				$ 15,600,000
Belmont
ACQUISITIONS
Voting interest acquired (as a percent)				100.00%
Total consideration paid				$ 4,600,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable				200,000
Prepaid and other current assets				100,000
Property and equipment				1,600,000
Goodwill				2,400,000
Intangible assets				1,800,000
Deferred tax liability				(1,300,000)
Accounts payable and other liabilities				(300,000)
Total				$ 4,500,000
Amortization expense adjustment															100,000
Previous quarter amortziation expense															62,566
Accumulated amortization adjustment															100,000
Increase (decrease) in goodwill															600,000
Increase (decrease) in deferred tax liability															600,000
Deferred tax benefit due to TCJA															400,000
Belmont | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															200,000
Belmont | Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															1,200,000
Belmont | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															300,000
Moore Freight Service
ACQUISITIONS
Voting interest acquired (as a percent)					100.00%
Total consideration paid					$ 59,100,000
Cash payments for business consideration					$ 35,100,000
Number of shares transferred | shares					145,129
Common stock issued in acquisitions					$ 1,800,000
Outstanding debt assumed					22,200,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable					4,500,000
Parts supplies					300,000
Prepaid and other current assets					300,000
Property and equipment					22,000,000
Goodwill					17,300,000
Intangible assets					30,400,000
Other long-term assets					100,000
Deferred tax liability					(13,800,000)
Accounts payable and other liabilities					(1,900,000)
Total					59,200,000
Increase (decrease) in intangible assets due to valuation													(500,000)
Transaction expenses incurred, not deductible for taxes purposes					$ 600,000
Amortization expense adjustment															1,500,000
Previous quarter amortziation expense															900,000
Accumulated amortization adjustment															1,500,000
Increase (decrease) in goodwill															11,700,000
Deferred tax benefit due to TCJA													200,000		4,000,000
Moore Freight Service | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															3,500,000
Moore Freight Service | Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															23,700,000
Moore Freight Service | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Indefinite lived intangibles															3,200,000
Roadmaster Group
ACQUISITIONS
Voting interest acquired (as a percent)					100.00%
Total consideration paid					$ 86,900,000
Cash payments for business consideration					$ 37,500,000
Number of shares transferred | shares					3,114,247
Common stock issued in acquisitions					$ 39,100,000
Outstanding debt assumed					10,300,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable					9,800,000
Parts supplies					200,000
Prepaid and other current assets					1,100,000
Property and equipment					36,800,000
Goodwill					51,700,000
Intangible assets					22,900,000
Other long-term assets					700,000
Deferred tax liability					(10,000,000)
Accounts payable and other liabilities					(26,800,000)
Total					86,400,000
Increase (decrease) in intangible assets due to valuation													9,400,000
Transaction expenses incurred, not deductible for taxes purposes					$ 600,000
Amortization expense adjustment															600,000
Previous quarter amortziation expense															300,000
Accumulated amortization adjustment															600,000
Increase (decrease) in goodwill															8,700,000
Increase (decrease) in deferred tax liability															8,700,000
Deferred tax benefit due to TCJA													3,500,000		3,000,000
Roadmaster Group | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															2,900,000
Roadmaster Group | Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															7,300,000
Roadmaster Group | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Indefinite lived intangibles															12,700,000
Tennessee Steel Haulers and Co
ACQUISITIONS
Voting interest acquired (as a percent)					100.00%
Total consideration paid					$ 91,900,000
Cash payments for business consideration					$ 74,900,000
Number of shares transferred | shares					972,680
Common stock issued in acquisitions					$ 12,000,000
Outstanding debt assumed					5,000,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable					20,200,000
Prepaid and other current assets					5,900,000
Property and equipment					8,700,000
Goodwill					34,600,000
Intangible assets					49,900,000
Other long-term assets					19,000,000
Deferred tax liability					(32,600,000)
Accounts payable and other liabilities					(14,000,000)
Total					91,700,000
Increase (decrease) in intangible assets due to valuation													5,900,000
Transaction expenses incurred, not deductible for taxes purposes					$ 500,000
Amortization expense adjustment															2,100,000
Previous quarter amortziation expense															1,200,000
Accumulated amortization adjustment															2,100,000
Increase (decrease) in goodwill															19,200,000
Increase (decrease) in deferred tax liability															19,200,000
Deferred tax benefit due to TCJA													1,600,000		6,600,000
Tennessee Steel Haulers and Co | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															12,400,000
Tennessee Steel Haulers and Co | Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles															15,900,000
Tennessee Steel Haulers and Co | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Indefinite lived intangibles															21,500,000
RandR Trucking Holdings, LLC
ACQUISITIONS
Voting interest acquired (as a percent)						100.00%
Total consideration paid						$ 38,400,000
Cash payments for business consideration						24,600,000
Outstanding debt assumed						13,800,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable						5,100,000
Parts supplies						100,000
Prepaid and other current assets						1,500,000
Property and equipment						16,900,000
Goodwill						15,700,000
Intangible assets						11,000,000
Other long-term assets						200,000
Deferred tax liability						(8,900,000)
Accounts payable and other liabilities						(3,400,000)
Total						38,200,000
Transaction expenses incurred, not deductible for taxes purposes						$ 600,000
The Steelman Companies
ACQUISITIONS
Voting interest acquired (as a percent)							100.00%
Total consideration paid							$ 18,800,000
Cash payments for business consideration							$ 11,200,000
Number of shares transferred | shares							746,170
Recognized Identifiable Assets Acquired And Liabilities Assumed Intangible Assets							$ 14,900,000
Common stock issued in acquisitions							7,600,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable							4,400,000
Parts supplies							100,000
Prepaid and other current assets							2,300,000
Property and equipment							11,100,000
Goodwill							9,700,000
Intangible assets							6,600,000
Other long-term assets							5,000,000
Deferred tax liability							(4,800,000)
Accounts payable and other liabilities							(15,600,000)
Total							18,800,000
Transaction expenses incurred, not deductible for taxes purposes							$ 300,000
Increase (decrease) in goodwill															1,700,000
Increase (decrease) in deferred tax liability															1,700,000
Deferred tax benefit due to TCJA															(600,000)
Schilli Transportation Services Inc
ACQUISITIONS
Voting interest acquired (as a percent)								100.00%
Total consideration paid								$ 27,400,000
Cash payments for business consideration								$ 21,000,000
Number of shares transferred | shares								232,885
Common stock issued in acquisitions								$ 2,300,000
Outstanding debt assumed								4,000,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable								8,600,000
Parts supplies								1,700,000
Prepaid and other current assets								2,500,000
Property and equipment								39,900,000
Goodwill								11,100,000
Intangible assets								6,000,000
Other long-term assets								900,000
Deferred tax liability								(15,400,000)
Accounts payable and other liabilities								(27,900,000)
Total								27,400,000
Transaction expenses incurred, not deductible for taxes purposes								$ 400,000
Increase (decrease) in goodwill															2,800,000
Decrease in receivables															(900,000)
Decrease in assets held-for-sale															300,000
Decrease in fixed assets															1,600,000
Increase (decrease) in deferred tax liability															700,000
Big Freight Systems Inc
ACQUISITIONS
Voting interest acquired (as a percent)								100.00%
Total consideration paid								$ 16,700,000
Cash payments for business consideration								$ 12,400,000
Number of shares transferred | shares								109,248
Common stock issued in acquisitions								$ 1,100,000
EBITDA multiplier								0.4
Contingent liability								1,100,000
Outstanding debt assumed								3,200,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable								4,900,000
Parts supplies								200,000
Prepaid and other current assets								300,000
Property and equipment								11,500,000
Goodwill								7,700,000
Intangible assets								4,200,000
Other long-term assets								100,000
Deferred tax liability								(4,800,000)
Accounts payable and other liabilities								(6,300,000)
Total								17,800,000
Transaction expenses incurred, not deductible for taxes purposes								$ 600,000
Increase (decrease) in goodwill															600,000
Foreign currency translation adjustment															$ 300,000
Acquisition 2018
ACQUISITIONS
Revenue																			163,600,000
Net income (loss)																			1,500,000
Builders
ACQUISITIONS
Voting interest acquired (as a percent)	100.00%
Total consideration paid	$ 36,300,000
Cash payments for business consideration	$ 30,000,000
Number of shares transferred | shares	399,530
Common stock issued in acquisitions	$ 3,400,000
Outstanding debt assumed	2,900,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable													8,400,000				8,400,000		8,400,000
Parts supplies													300,000				300,000		300,000
Prepaid and other current assets													1,500,000				1,500,000		1,500,000
Property and equipment													29,400,000				29,400,000		29,400,000
Goodwill													14,700,000				14,700,000		14,700,000
Intangible assets	13,100,000												10,600,000				10,600,000		10,600,000
Other long-term assets													500,000				500,000		500,000
Deferred tax liability													(9,200,000)				(9,200,000)		(9,200,000)
Accounts payable and other liabilities													(19,900,000)				(19,900,000)		(19,900,000)
Total													36,300,000				36,300,000		36,300,000
Provisional intangible assets																			(2,500,000)
Transaction expenses incurred, not deductible for taxes purposes	$ 200,000
Amortization expense adjustment													200,000
Previous quarter amortziation expense													100,000
Accumulated amortization adjustment													200,000				200,000		200,000
Increase (decrease) in goodwill													400,000						2,500,000
Increase (decrease) in deferred tax liability													400,000
Builders | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles													500,000				500,000		500,000
Builders | Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles													5,100,000				5,100,000		5,100,000
Builders | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Indefinite lived intangibles													5,000,000				5,000,000		5,000,000
Aveda
ACQUISITIONS
Total consideration paid			$ 118,700,000
Cash payments for business consideration			$ 27,300,000
Number of shares transferred | shares			1,612,979
Common stock issued in acquisitions			$ 15,400,000
Contingent liability			21,200,000
Outstanding debt assumed			54,800,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable													37,300,000				37,300,000		37,300,000
Prepaid and other current assets													2,500,000				2,500,000		2,500,000
Property and equipment													89,800,000				89,800,000		89,800,000
Goodwill													7,700,000				7,700,000		7,700,000
Intangible assets			$ 9,000,000										15,000,000				15,000,000		15,000,000
Indefinite lived intangibles													15,000,000				15,000,000		15,000,000
Deferred tax liability													(6,700,000)				(6,700,000)		(6,700,000)
Accounts payable and other liabilities													(30,000,000)				(30,000,000)		(30,000,000)
Total													115,600,000				115,600,000		115,600,000
Cash per common share | $ / shares			$ 0.45
Provisional intangible assets																			6,100,000
Transaction expenses incurred, not deductible for taxes purposes			$ 1,100,000
Increase (decrease) in goodwill												700,000	700,000						4,700,000
Increase (decrease) in deferred tax liability												700,000	700,000						4,700,000
Aveda | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles													1,500,000				1,500,000		1,500,000
Aveda | Customer relationships
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles													7,200,000				7,200,000		7,200,000
Aveda | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Indefinite lived intangibles													6,300,000				6,300,000		6,300,000
Kelsey Trail
ACQUISITIONS
Voting interest acquired (as a percent)		100.00%
Total consideration paid		$ 6,200,000
Cash payments for business consideration		$ 5,300,000
Number of shares transferred | shares		95,859
Common stock issued in acquisitions		$ 900,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable													2,300,000				2,300,000		2,300,000
Prepaid and other current assets													400,000				400,000		400,000
Property and equipment													9,200,000				9,200,000		9,200,000
Goodwill													3,300,000				3,300,000		3,300,000
Intangible assets		1,900,000											1,500,000				1,500,000		1,500,000
Indefinite lived intangibles													1,600,000				1,600,000		1,600,000
Deferred tax liability													(2,700,000)				(2,700,000)		(2,700,000)
Accounts payable and other liabilities													(8,000,000)				(8,000,000)		(8,000,000)
Total													6,000,000				6,000,000		6,000,000
Provisional intangible assets																			(300,000)
Transaction expenses incurred, not deductible for taxes purposes		$ 100,000
Increase (decrease) in goodwill												(900,000)	2,500,000				300,000
Increase (decrease) in deferred tax liability												$ (900,000)	2,500,000
Kelsey Trail | Non-compete agreements
Allocation of the purchase price paid to the fair values of the net assets
Finite lived intangibles													100,000				100,000		100,000
Kelsey Trail | Trade names
Allocation of the purchase price paid to the fair values of the net assets
Indefinite lived intangibles													1,500,000				1,500,000		1,500,000
Leavitts Freight Service [Member]
ACQUISITIONS
Voting interest acquired in asset acquisition (as a percent)	100.00%
Total consideration paid in an asset acquisition	$ 14,900,000
Leavitts Freight Service [Member] | Fair Value, Nonrecurring [Member]
ACQUISITIONS
Finite-lived Intangible Assets, Fair Value Disclosure	5,200,000
Allocation of the purchase price paid to the fair values of the net assets
Accounts receivable.													1,900,000				1,900,000		1,900,000
Parts supply													100,000				100,000		100,000
Prepaid and other current assets													400,000				400,000		400,000
Property and equipment													8,500,000				8,500,000		8,500,000
Goodwill													5,100,000				5,100,000		5,100,000
Intangible assets													3,600,000				3,600,000		3,600,000
Accounts payable and other liabilities													(4,900,000)				(4,900,000)		(4,900,000)
Total													14,700,000				14,700,000		14,700,000
Increase (decrease) in intangible assets due to valuation																			(1,600,000)
Tax deductible transaction expenses	$ 300,000
Leavitts Freight Service [Member] | Fair Value, Nonrecurring [Member] | Non-compete agreements
ACQUISITIONS
Finite-lived Intangible Assets, Fair Value Disclosure													500,000				500,000		500,000
Leavitts Freight Service [Member] | Fair Value, Nonrecurring [Member] | Customer relationships
ACQUISITIONS
Finite-lived Intangible Assets, Fair Value Disclosure													1,300,000				1,300,000		1,300,000
Leavitts Freight Service [Member] | Fair Value, Nonrecurring [Member] | Trade names
ACQUISITIONS
Finite-lived Intangible Assets, Fair Value Disclosure													$ 1,800,000				$ 1,800,000		$ 1,800,000