Quarterly Results (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2013
Selected Quarterly Financial Information [Abstract]
Revenues	$ 1,596,221	$ 1,651,332	$ 1,691,553	$ 1,677,526	$ 1,768,830	$ 1,705,105	$ 1,599,141	$ 1,491,645	$ 6,616,632		$ 6,564,721		$ 6,080,257
Net revenues	536,169	569,981	552,141	529,486	518,871	513,256	484,714	464,586	2,187,777	[1]	1,981,427	[1]	1,882,853	[1]
Net earnings	115,100	118,736	118,329	107,332	100,740	102,797	91,728	84,195	459,497		379,460		350,011
Net earnings attributable to shareholders	$ 114,449	$ 118,310	$ 117,760	$ 106,704	$ 99,381	$ 102,381	$ 91,302	$ 83,824	$ 457,223		$ 376,888		$ 348,526
Diluted earnings attributable to shareholders per share	$ 0.61	$ 0.62	$ 0.61	$ 0.55	$ 0.51	$ 0.53	$ 0.46	$ 0.42	$ 2.40		$ 1.92		$ 1.68
Basic earnings attributable to shareholders per share	$ 0.62	$ 0.63	$ 0.62	$ 0.56	$ 0.52	$ 0.53	$ 0.46	$ 0.42	$ 2.42		$ 1.92		$ 1.69

[1] Net revenues are a non-GAAP measure calculated as revenues less directly related operations expenses attributable to the Company's principal services. The Company's management believes that net revenues are a better measure than total revenues when evaluating the Company's operating segment performance since total revenues earned as a freight consolidator include the carriers' charges for carrying the shipment, whereas revenues earned in other capacities include primarily the commissions and fees earned by the Company. Net revenue is one of the Company's primary operational and financial measures and demonstrates the Company's ability to concentrate and leverage purchasing power through effective consolidation of shipments from customers utilizing a variety of transportation carriers and optimal routings.