Acquisitions - Pro Forma (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended									12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012		Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Business Acquisition [Line Items]
Revenues	$ 3,152,882	$ 3,316,665	$ 3,288,262	$ 2,994,267	$ 2,970,876	[1]	$ 2,880,409	$ 2,955,714	$ 2,552,114	$ 12,752,076	$ 11,359,113	$ 10,336,346
Business Acquisition, Pro Forma Revenue											12,010,326	11,090,444
Operating Income (Loss)	155,113	176,355	182,476	168,706	133,604	[1]	187,257	184,914	169,545	682,650	675,320	692,730
Business Acquisition, Pro Forma Operating Income (Loss)											678,873	705,067
Net Income (Loss) Attributable to Parent	92,952	107,737	111,872	103,343	256,392	[1]	116,330	114,582	106,500	415,904	593,804	431,612
Business Acquisition, Pro Forma Net Income (Loss)											592,976	440,463
Phoenix
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Revenue											692,836	803,358
Business Acquisition, Pro Forma Operating Income (Loss)											24,131	36,906
Business Acquisition, Pro Forma Net Income (Loss)											11,976	24,150
Business Acquisition, Pro Forma Elimination Personnel Costs from Purchased Transportation and Related Services											(24,422)	(29,028)
Business Acquisition, Pro Forma Elimination Personnel Costs from Selling, General and Administrative Services											(50,065)	(54,209)
Business Acquisition, Pro Forma Reclassify Costs to Personnel Expenses											74,487	83,237
Business Acquisition, Pro Forma Compensation Related Expenses											(5,080)	(4,060)
Business Acquisition, Pro Forma Amortization Expense											13,555	16,265
Business Acquisition, Pro Forma Rent Expense											280	329
Business Acquisition, Pro Forma Depreciation Expense											123	150
Business Acquisition, Pro Forma Interest Expense											(2,127)	(2,574)
Business Acquisition, Pro Forma Additional Bonus Paid by Seller											(1,400)	0
Business Acquisition, Pro Forma Advisory Fees Paid by Seller											(582)	0
Business Acquisition, Pro Forma Elimination of Variable Interest Entities Not Acquired											215	220
Business Acquisition, Pro Forma Consolidated Effective Tax Rate											(1,487)	(1,842)
T-Chek
Business Acquisition [Line Items]
Business Divestiture, Pro Forma Revenue											(41,623)	(49,260)
Business Divestiture, Pro Forma Operating Income (Loss)											(20,578)	(24,569)
Business Divestiture, Pro Forma Net Income (Loss)											$ (12,804)	$ (15,299)

[1] The Company's results for the fourth quarter of 2012 were effected by certain significant event-specific charges or credits related to our acquisitions and divestitures. See "Reported to Adjusted Statements of Operations Data" in Selected Financial Data in Item 6 and Management's Discussion and Analysis of Financial Condition and Results of Operations in Item 7 of Part II of this report.