Organization Nature of Business and Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Segment Units	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Organization Nature of Business and Significant Accounting Policies [Abstract]
Number of operating segments | Segment	3
Excess tax benefit, amount		$ 500	$ 1,200
Debt issuance costs	$ 3,485	4,861
Number of reporting units | Units	4
Impairment charges	$ 4,402	373,661	0
Non-cash impairment charges	1,600
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	18,573	14,026	10,775
Divestiture of Unitrans	(91)		0
Provision, charged to expense	5,964	5,127	4,816
Write-off, less recoveries	(13,555)	(580)	(1,565)
Ending balance	$ 10,891	18,573	14,026
Vesting period	4 years
Minimum
Allowance for Doubtful Accounts Receivable [Roll Forward]
Vesting period	3 years
Maximum
Allowance for Doubtful Accounts Receivable [Roll Forward]
Vesting period	5 years
Buildings and leasehold improvements | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful lives	5 years
Buildings and leasehold improvements | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful lives	40 years
Computer equipment and software | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful lives	3 years
Computer equipment and software | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful lives	10 years
Office equipment, furniture, and fixtures | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful lives	3 years
Office equipment, furniture, and fixtures | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful lives	10 years
Dock, warehouse, and other equipment | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful lives	5 years
Dock, warehouse, and other equipment | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful lives	7 years
Tractors and trailers | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful lives	3 years
Tractors and trailers | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful lives	15 years
Aircraft fleet and rotable spare parts | Minimum
Property, Plant and Equipment [Abstract]
Estimated useful lives	3 years
Aircraft fleet and rotable spare parts | Maximum
Property, Plant and Equipment [Abstract]
Estimated useful lives	8 years
TL
Organization Nature of Business and Significant Accounting Policies [Abstract]
Number of reporting units | Units	1
Impairment charges	$ 0	159,118	0
LTL
Organization Nature of Business and Significant Accounting Policies [Abstract]
Number of reporting units | Units	1
Impairment charges	$ 0	$ 197,312	$ 0
Global Solutions
Organization Nature of Business and Significant Accounting Policies [Abstract]
Number of reporting units | Units	2
Central Minnesota Logistics, Inc.
Organization Nature of Business and Significant Accounting Policies [Abstract]
Equity method investment ownership percentage	37.50%
Accounting Standards Update 2014-09 | Minimum
Organization Nature of Business and Significant Accounting Policies [Abstract]
Revenues	$ 1,000
Customer Relationships [Member] | Minimum
Organization Nature of Business and Significant Accounting Policies [Abstract]
Period of amortization of intangible assets	5 years
Customer Relationships [Member] | Maximum
Organization Nature of Business and Significant Accounting Policies [Abstract]
Period of amortization of intangible assets	12 years