Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	$ 2,035,579	$ 1,957,559	$ 4,055,630	$ 3,811,821
Net revenues	[2]	661,695	642,546	1,315,809	1,278,384
Operating income		192,201	183,584	379,802	376,402
Identifiable assets at period end		3,646,990	3,132,832	3,646,990	3,132,832		$ 3,314,559
Capital expenditures		12,987	12,113	22,422	25,909
Depreciation and amortization		12,677	13,576	26,070	27,498
Equity		2,052,394	1,892,559	2,052,394	1,892,559	$ 2,125,434	$ 1,987,720	$ 1,982,266	$ 1,994,373
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	(764)	(71,914)	(1,482)	(139,854)
Net revenues	[2]	(370)	(971)	(460)	(960)
Operating income		(6)	(3)	(14)	8
Identifiable assets at period end		(7,368)	(5,997)	(7,368)	(5,997)
Equity		(33,199)	(34,291)	(33,199)	(34,291)
Operating Segments | United States Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	681,076	598,076	1,340,859	1,161,826
Net revenues	[2]	294,983	271,880	587,412	549,065
Operating income		87,923	63,628	161,936	133,276
Identifiable assets at period end		1,819,718	1,488,060	1,819,718	1,488,060
Capital expenditures		8,985	6,032	15,900	9,203
Depreciation and amortization		7,687	8,447	15,909	17,212
Equity		1,303,381	1,196,226	1,303,381	1,196,226
Operating Segments | Other North America Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	85,537	84,244	176,947	164,331
Net revenues	[2]	35,201	34,749	70,370	65,196
Operating income		8,858	10,077	19,818	19,095
Identifiable assets at period end		176,151	153,827	176,151	153,827
Capital expenditures		768	2,191	996	3,719
Depreciation and amortization		459	473	926	871
Equity		83,417	56,702	83,417	56,702
Operating Segments | Latin America Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	38,757	42,618	72,936	78,727
Net revenues	[2]	16,714	15,923	31,777	30,668
Operating income		2,346	2,701	4,982	5,071
Identifiable assets at period end		73,197	54,186	73,197	54,186
Capital expenditures		145	167	238	672
Depreciation and amortization		380	395	812	763
Equity		31,014	26,625	31,014	26,625
Operating Segments | North Asia Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	621,951	680,227	1,254,804	1,316,816
Net revenues	[2]	134,397	140,583	268,604	277,791
Operating income		64,453	70,359	130,233	140,282
Identifiable assets at period end		580,311	540,954	580,311	540,954
Capital expenditures		300	559	644	1,343
Depreciation and amortization		1,384	1,303	2,791	2,679
Equity		282,192	250,513	282,192	250,513
Operating Segments | South Asia Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	181,380	179,528	358,559	354,678
Net revenues	[2]	48,893	44,886	96,262	89,292
Operating income		15,513	13,374	31,420	28,506
Identifiable assets at period end		193,771	157,479	193,771	157,479
Capital expenditures		428	695	604	1,024
Depreciation and amortization		496	542	1,032	1,125
Equity		107,229	112,259	107,229	112,259
Operating Segments | Europe Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	319,331	330,775	632,021	650,755
Net revenues	[2]	98,655	102,371	195,450	201,006
Operating income		9,315	16,958	23,267	36,236
Identifiable assets at period end		581,518	526,607	581,518	526,607
Capital expenditures		1,914	1,225	2,896	8,416
Depreciation and amortization		1,775	1,955	3,606	3,931
Equity		168,570	157,493	168,570	157,493
Operating Segments | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax	[1]	108,311	114,005	220,986	224,542
Net revenues	[2]	33,222	33,125	66,394	66,326
Operating income		3,799	6,490	8,160	13,928
Identifiable assets at period end		229,692	217,716	229,692	217,716
Capital expenditures		447	1,244	1,144	1,532
Depreciation and amortization		496	461	994	917
Equity		$ 109,790	$ 127,032	$ 109,790	$ 127,032

[1] 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 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 net revenues or 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 net revenues. The impact of these changes on reported segment revenues was immaterial and prior year segment revenues have not been revised.

[2] Net revenues are a non-GAAP measure calculated as revenues less directly related operating 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.