ACQUISITIONS (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Jan. 01, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Revenues		$ 3,419,253	$ 3,467,362	$ 10,265,231	$ 10,112,865
Revenues, pro forma			3,632,563		10,581,772
Income from operations		$ 232,711	203,337	$ 643,731	560,690
Income from operations, pro forma			211,053		577,283
Freightquote
Business Acquisition [Line Items]
Total purchase price	$ 398,600
Estimated life				5 years
Identifiable intangible assets	37,800
Revenues			165,201		468,907
Income from operations			7,716		16,593
Freightquote | Acquisition-related Costs
Business Acquisition [Line Items]
Additional amortization expense on identifiable intangible assets			(1,890)		(5,670)
Other			$ 1,009		$ 2,948
Freightquote | Trademarks
Business Acquisition [Line Items]
Acquired trademarks value	8,600
Freightquote | Customer relationships
Business Acquisition [Line Items]
Identifiable intangible assets	37,500
Freightquote | Noncompete agreements
Business Acquisition [Line Items]
Identifiable intangible assets	$ 300