Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) - USD ($) $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Segment Reporting Information [Line Items]
Total revenues		$ 1,901,371	$ 1,802,166	$ 1,672,279	$ 1,545,132	$ 1,642,007	$ 1,562,394	$ 1,475,164	$ 1,418,472	$ 6,920,948		$ 6,098,037		$ 6,616,632
Net revenues		628,809	$ 599,142	$ 563,633	$ 527,605	548,591	$ 545,259	$ 553,117	$ 517,069	2,319,189	[1]	2,164,036	[1]	2,187,777	[1]
Operating income										700,260		670,163		721,484
Identifiable assets at year end		3,117,008				2,790,871				3,117,008		2,790,871		2,565,577
Capital expenditures										95,016		59,316		44,383
Depreciation and amortization										49,310		46,796		46,012
Equity		1,994,373				1,847,213				1,994,373		1,847,213		1,694,676		$ 1,871,608
United States Segment
Segment Reporting Information [Line Items]
Total revenues										1,851,395		1,683,006		1,763,361
Other North America Segment
Segment Reporting Information [Line Items]
Total revenues										256,359		226,561		226,284
Latin America Segment
Segment Reporting Information [Line Items]
Total revenues										97,096		84,665		94,229
North Asia Segment
Segment Reporting Information [Line Items]
Total revenues										2,576,971		2,242,670		2,557,398
South Asia Segment
Segment Reporting Information [Line Items]
Total revenues										661,878		603,980		677,628
Europe Segment
Segment Reporting Information [Line Items]
Total revenues										1,072,028		918,561		958,827
Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues										405,221		338,594		338,905
Geography Eliminations | United States Segment
Segment Reporting Information [Line Items]
Total revenues										(111,163)		(106,076)		(118,884)
Geography Eliminations | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues										(11,827)		(10,778)		(13,383)
Geography Eliminations | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues										(14,766)		(15,037)		(19,158)
Geography Eliminations | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues										(21,405)		(21,212)		(21,722)
Geography Eliminations | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues										(22,999)		(24,251)		(25,018)
Geography Eliminations | Europe Segment
Segment Reporting Information [Line Items]
Total revenues										(43,296)		(41,102)		(42,787)
Geography Eliminations | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues										(20,848)		(21,876)		(21,322)
Operating Segments | United States Segment
Segment Reporting Information [Line Items]
Total revenues										1,962,558		1,789,082		1,882,245
Net revenues	[1]									1,008,841		918,110		906,780
Operating income										277,821		250,715		245,257
Identifiable assets at year end		1,595,140				1,455,722				1,595,140		1,455,722		1,185,671
Capital expenditures										28,212		39,531		26,807
Depreciation and amortization										32,017		29,939		29,532
Equity		1,337,568				1,166,582				1,337,568		1,166,582		986,330
Operating Segments | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues										268,186		237,339		239,667
Net revenues	[1]									119,071		119,492		124,381
Operating income										38,131		32,530		46,846
Identifiable assets at year end		151,181				104,804				151,181		104,804		111,549
Capital expenditures										1,563		1,727		3,915
Depreciation and amortization										1,546		1,479		1,331
Equity		60,705				46,448				60,705		46,448		70,932
Operating Segments | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues										111,862		99,702		113,387
Net revenues	[1]									58,199		56,066		65,017
Operating income										9,964		13,321		19,656
Identifiable assets at year end		55,431				49,231				55,431		49,231		48,678
Capital expenditures										4,612		1,038		1,756
Depreciation and amortization										1,277		1,187		1,041
Equity		26,546				27,164				26,546		27,164		33,161
Operating Segments | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues										2,598,376		2,263,882		2,579,120
Net revenues	[1]									509,235		471,275		493,235
Operating income										248,422		230,777		245,854
Identifiable assets at year end		458,152				511,851				458,152		511,851		446,914
Capital expenditures										3,756		3,889		2,203
Depreciation and amortization										5,326		5,455		5,425
Equity		240,721				327,672				240,721		327,672		253,097
Operating Segments | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues										684,877		628,231		702,646
Net revenues	[1]									163,450		171,033		179,110
Operating income										53,057		64,967		69,643
Identifiable assets at year end		137,279				120,300				137,279		120,300		127,014
Capital expenditures										1,688		3,038		2,383
Depreciation and amortization										2,215		2,177		2,110
Equity		94,516				91,983				94,516		91,983		99,220
Operating Segments | Europe Segment
Segment Reporting Information [Line Items]
Total revenues										1,115,324		959,663		1,001,614
Net revenues	[1]									335,702		304,429		308,301
Operating income										48,491		42,195		65,024
Identifiable assets at year end		501,711				351,960				501,711		351,960		421,590
Capital expenditures										53,954		7,554		5,222
Depreciation and amortization										5,068		4,576		4,931
Equity		142,971				108,430				142,971		108,430		154,174
Operating Segments | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues										426,069		360,470		360,227
Net revenues	[1]									121,267		123,335		110,953
Operating income										24,365		35,672		29,204
Identifiable assets at year end		215,495				190,902				215,495		190,902		221,835
Capital expenditures										1,231		2,539		2,097
Depreciation and amortization										1,861		1,983		1,642
Equity		123,600				112,633				123,600		112,633		130,105
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenues										(246,304)		(240,332)		(262,274)
Net revenues	[1]									3,424		296
Operating income										9		(14)
Identifiable assets at year end		2,619				6,101				2,619		6,101		2,326
Equity		$ (32,254)				$ (33,699)				$ (32,254)		$ (33,699)		$ (32,343)

[1] 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.