ACQUISITIONS (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2015	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Business Acquisition [Line Items]
Revenues		$ 3,545,088	$ 3,502,918	$ 6,845,978	$ 6,645,503
Revenues, pro forma			3,665,562		6,949,211
Income from operations		$ 229,095	200,382	$ 411,020	357,353
Income from operations, pro forma			205,549		366,230
Freightquote
Business Acquisition [Line Items]
Total purchase price	$ 398,400
Estimated life				5 years
Identifiable intangible assets	37,800
Revenues			162,644		303,708
Income from operations			5,167		8,877
Freightquote | Acquisition-related Costs
Business Acquisition [Line Items]
Additional amortization expense on identifiable intangible assets			(1,890)		(3,780)
Other			$ 1,142		$ 1,939
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