Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Total revenues		$ 1,651,332	$ 1,705,105	$ 5,020,411	$ 4,795,891
Net revenues	[1]	569,981	513,256	1,651,608	1,462,556
Operating income		191,893	159,131	543,492	436,777
Identifiable assets at period end		2,827,018	2,926,053	2,827,018	2,926,053	$ 2,890,905
Capital expenditures		9,546	8,255	31,903	26,650
Depreciation and amortization		11,475	12,741	34,424	37,540
Equity		1,842,192	1,903,930	1,842,192	1,903,930	$ 1,871,608	$ 2,086,331
United States Segment
Segment Reporting Information [Line Items]
Total revenues		441,097	438,882	1,334,900	1,256,075
Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		56,818	55,209	170,351	162,136
Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		24,681	22,962	73,076	65,594
North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		648,096	670,763	1,943,441	1,863,077
South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		158,011	174,839	524,254	468,152
Europe Segment
Segment Reporting Information [Line Items]
Total revenues		234,334	259,960	716,373	744,466
Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		88,295	82,490	258,016	236,391
Geography Eliminations | United States Segment
Segment Reporting Information [Line Items]
Total revenues		29,168	24,847	89,329	67,266
Geography Eliminations | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		3,492	2,867	9,991	7,829
Geography Eliminations | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		4,991	5,194	15,171	15,965
Geography Eliminations | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		5,206	6,116	16,330	17,170
Geography Eliminations | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		6,289	6,814	18,677	20,072
Geography Eliminations | Europe Segment
Segment Reporting Information [Line Items]
Total revenues		11,125	9,783	31,478	28,931
Geography Eliminations | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		5,459	5,171	15,638	14,638
Operating Segments | United States Segment
Segment Reporting Information [Line Items]
Total revenues		470,265	463,729	1,424,229	1,323,341
Net revenues	[1]	232,912	215,320	681,868	607,508
Operating income		65,389	68,972	193,117	180,650
Identifiable assets at period end		1,385,157	1,333,124	1,385,157	1,333,124
Capital expenditures		6,196	3,171	20,232	12,646
Depreciation and amortization		7,439	8,369	22,171	24,100
Equity		1,144,466	1,074,837	1,144,466	1,074,837
Operating Segments | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		60,310	58,076	180,342	169,965
Net revenues	[1]	32,713	27,323	93,967	79,017
Operating income		11,905	7,779	33,433	23,155
Identifiable assets at period end		108,644	113,621	108,644	113,621
Capital expenditures		658	361	2,602	1,047
Depreciation and amortization		363	303	965	879
Equity		64,384	75,848	64,384	75,848
Operating Segments | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		29,672	28,156	88,247	81,559
Net revenues	[1]	17,115	16,792	51,159	48,797
Operating income		5,007	4,890	15,804	14,425
Identifiable assets at period end		56,987	53,939	56,987	53,939
Capital expenditures		222	369	1,408	841
Depreciation and amortization		268	226	784	665
Equity		35,890	34,218	35,890	34,218
Operating Segments | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		653,302	676,879	1,959,771	1,880,247
Net revenues	[1]	135,488	106,225	377,384	297,117
Operating income		69,690	45,153	187,343	124,528
Identifiable assets at period end		472,189	580,260	472,189	580,260
Capital expenditures		711	1,648	1,476	5,691
Depreciation and amortization		1,336	1,493	4,114	4,471
Equity		250,362	341,092	250,362	341,092
Operating Segments | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		164,300	181,653	542,931	488,224
Net revenues	[1]	45,970	42,023	135,114	121,261
Operating income		18,574	12,073	48,594	36,371
Identifiable assets at period end		140,206	152,236	140,206	152,236
Capital expenditures		291	1,247	1,599	2,221
Depreciation and amortization		531	523	1,609	1,739
Equity		103,457	111,556	103,457	111,556
Operating Segments | Europe Segment
Segment Reporting Information [Line Items]
Total revenues		245,459	269,743	747,851	773,397
Net revenues	[1]	77,250	80,024	229,745	234,313
Operating income		14,188	14,921	44,846	41,515
Identifiable assets at period end		427,053	476,799	427,053	476,799
Capital expenditures		1,223	1,016	3,292	3,116
Depreciation and amortization		1,120	1,391	3,542	4,376
Equity		148,287	185,332	148,287	185,332
Operating Segments | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		93,754	87,661	273,654	251,029
Net revenues	[1]	28,533	25,549	82,371	74,543
Operating income		7,140	5,343	20,355	16,133
Identifiable assets at period end		229,670	204,378	229,670	204,378
Capital expenditures		245	443	1,294	1,088
Depreciation and amortization		418	436	1,239	1,310
Equity		126,321	114,229	126,321	114,229
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenues		(65,730)	(60,792)	(196,614)	(171,871)
Identifiable assets at period end		7,112	11,696	7,112	11,696
Equity		$ (30,975)	$ (33,182)	$ (30,975)	$ (33,182)

[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.