Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues		$ 1,545,132	$ 1,418,472
Net revenues	[1]	527,605	517,069
Operating income		146,114	151,826
Identifiable assets at period end		2,902,719	2,661,540	$ 2,790,871
Capital expenditures		12,761	14,035
Depreciation and amortization		11,927	11,329
Equity		1,951,720	1,782,511	$ 1,847,213	$ 1,694,676
United States Segment
Segment Reporting Information [Line Items]
Total revenues		426,019	407,826
Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		59,899	52,106
Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		22,103	20,064
North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		566,428	497,232
South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		147,240	136,418
Europe Segment
Segment Reporting Information [Line Items]
Total revenues		231,457	221,897
Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		91,986	82,929
Geography Eliminations | United States Segment
Segment Reporting Information [Line Items]
Total revenues		24,313	26,034
Geography Eliminations | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		2,639	2,700
Geography Eliminations | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		3,635	3,601
Geography Eliminations | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		5,051	5,096
Geography Eliminations | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		5,431	5,806
Geography Eliminations | Europe Segment
Segment Reporting Information [Line Items]
Total revenues		9,322	10,361
Geography Eliminations | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		4,964	5,394
Operating Segments | United States Segment
Segment Reporting Information [Line Items]
Total revenues		450,332	433,860
Net revenues	[1]	230,785	220,698
Operating income		52,346	48,205
Identifiable assets at period end		1,536,520	1,236,896
Capital expenditures		5,242	8,137
Depreciation and amortization		7,753	7,332
Equity		1,192,601	978,426
Operating Segments | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		62,538	54,806
Net revenues	[1]	25,793	27,378
Operating income		5,051	7,291
Identifiable assets at period end		106,068	119,258
Capital expenditures		234	311
Depreciation and amortization		372	364
Equity		51,812	79,312
Operating Segments | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		25,738	23,665
Net revenues	[1]	14,916	13,733
Operating income		3,451	3,852
Identifiable assets at period end		50,344	56,334
Capital expenditures		255	485
Depreciation and amortization		320	253
Equity		27,248	37,325
Operating Segments | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		571,479	502,328
Net revenues	[1]	111,833	110,791
Operating income		53,352	55,218
Identifiable assets at period end		514,509	455,973
Capital expenditures		1,240	1,085
Depreciation and amortization		1,320	1,319
Equity		371,152	300,188
Operating Segments | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		152,671	142,224
Net revenues	[1]	37,995	39,518
Operating income		13,224	15,691
Identifiable assets at period end		122,765	133,940
Capital expenditures		373	655
Depreciation and amortization		531	512
Equity		105,726	115,606
Operating Segments | Europe Segment
Segment Reporting Information [Line Items]
Total revenues		240,779	232,258
Net revenues	[1]	75,958	74,541
Operating income		11,646	12,253
Identifiable assets at period end		379,853	438,711
Capital expenditures		5,078	2,119
Depreciation and amortization		1,171	1,098
Equity		118,211	167,726
Operating Segments | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		96,950	88,323
Net revenues	[1]	29,731	30,407
Operating income		7,043	9,313
Identifiable assets at period end		188,098	216,576
Capital expenditures		339	1,243
Depreciation and amortization		460	451
Equity		119,627	137,112
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenues		(55,355)	(58,992)
Net revenues	[1]	594	3
Operating income		1	3
Identifiable assets at period end		4,562	3,852
Equity		$ (34,657)	$ (33,184)

[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.