Quarterly Results (Unaudited) (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Selected Quarterly Financial Information [Abstract]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 2,044,941	[1]	$ 2,074,855	[1]	$ 2,035,579	[1]	$ 2,020,051	[1]	$ 2,235,597	[1]	$ 2,090,947	[1]	$ 1,957,559	[1]	$ 1,854,262	[1]	$ 8,175,426	[2]	$ 8,138,365	[2]	$ 6,920,948	[2]
Operating income	180,340	[1]	206,550	[1]	192,201	[1]	187,601	[1]	217,007	[1]	203,154	[1]	183,584	[1]	192,818	[1]	766,692		796,563		700,260
Net earnings	137,748		160,627		153,530		140,111		179,577		163,067		140,946		136,200		592,016		619,790		490,383
Net earnings attributable to shareholders	$ 137,326		$ 160,221		$ 153,149		$ 139,699		$ 179,210		$ 162,692		$ 140,605		$ 135,692		$ 590,395		$ 618,199		$ 489,345
Diluted earnings attributable to shareholders per share	$ 0.79		$ 0.92		$ 0.88		$ 0.80		$ 1.02		$ 0.92		$ 0.79		$ 0.76		$ 3.39		$ 3.48		$ 2.69
Basic earnings attributable to shareholders per share	$ 0.81		$ 0.94		$ 0.90		$ 0.81		$ 1.04		$ 0.94		$ 0.80		$ 0.77		$ 3.45		$ 3.55		$ 2.73

[1] The fourth quarter of 2019 was significantly impacted by declines in results in our China operations due to the slowing of trade to and from China, which impacted overall freight movement around the globe. The Company’s consolidated financial results are expected to be further impacted in 2020 due to the significance of its China operations and the effects of the recent outbreak of the Novel Coronavirus (COVID-19). See Note 12 for further detail. In the fourth quarter 2019 and 2018, the People's Republic of China, including Hong Kong, represented 25% and 31%, respectively, of the Company’s total revenues and 25% and 27%, respectively, of the Company’s total operating income.

[2] In 2019, the Company revised its process to record the transfer, between its geographic operating segments, of revenues and the directly related cost of transportation and other expenses for freight service transactions between Company origin and destination locations. This change better aligns revenue reporting with the location where the services are performed, as well as the transactional reporting being developed as part of the Company’s new accounting systems and processes. The change in presentation had no impact on consolidated or segment operating income. The 2019 results also include the effect of changing the presentation of certain import services from a net to a gross basis, which increased segment revenues and directly related operating expenses but did not change operating income. The impact of these changes on reported segment revenues was immaterial and prior year segment revenues have not been revised.