Business Segment Information - Financial Information Regarding Company's Operations by Geographic Area (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues		$ 1,672,279	$ 1,475,164	$ 3,217,411	$ 2,893,636
Net revenues	[1]	563,633	553,117	1,091,238	1,070,186
Operating income		168,240	178,864	314,354	330,690
Identifiable assets at period end		3,022,756	2,687,455	3,022,756	2,687,455	$ 2,790,871
Capital expenditures		20,380	13,279	33,141	27,314
Depreciation and amortization		12,042	11,642	23,969	22,971
Equity		1,978,637	1,779,505	1,978,637	1,779,505	$ 1,847,213	$ 1,694,676
United States Segment
Segment Reporting Information [Line Items]
Total revenues		452,217	417,735	878,236	825,561
Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		62,554	56,674	122,453	108,780
Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		23,463	21,169	45,566	41,233
North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		620,050	517,489	1,186,478	1,014,721
South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		157,698	151,890	304,938	288,308
Europe Segment
Segment Reporting Information [Line Items]
Total revenues		259,533	229,882	490,990	451,779
Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		96,764	80,325	188,750	163,254
Geography Eliminations | United States Segment
Segment Reporting Information [Line Items]
Total revenues		28,155	28,973	52,468	55,007
Geography Eliminations | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		2,825	2,671	5,464	5,371
Geography Eliminations | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		3,759	4,187	7,394	7,788
Geography Eliminations | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		4,835	5,385	9,886	10,481
Geography Eliminations | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		5,408	6,326	10,839	12,132
Geography Eliminations | Europe Segment
Segment Reporting Information [Line Items]
Total revenues		9,664	10,097	18,986	20,458
Geography Eliminations | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		5,034	5,507	9,998	10,901
Operating Segments | United States Segment
Segment Reporting Information [Line Items]
Total revenues		480,372	446,708	930,704	880,568
Net revenues	[1]	250,027	232,860	480,812	453,558
Operating income		64,265	67,214	116,611	115,419
Identifiable assets at period end		1,487,582	1,343,669	1,487,582	1,343,669
Capital expenditures		6,852	8,778	12,094	16,915
Depreciation and amortization		7,731	7,366	15,484	14,698
Equity		1,147,962	1,069,876	1,147,962	1,069,876
Operating Segments | Other North America Segment
Segment Reporting Information [Line Items]
Total revenues		65,379	59,345	127,917	114,151
Net revenues	[1]	28,173	30,815	53,966	58,193
Operating income		12,317	9,600	17,368	16,891
Identifiable assets at period end		129,830	84,358	129,830	84,358
Capital expenditures		569	445	803	756
Depreciation and amortization		386	380	758	744
Equity		61,957	38,638	61,957	38,638
Operating Segments | Latin America Segment
Segment Reporting Information [Line Items]
Total revenues		27,222	25,356	52,960	49,021
Net revenues	[1]	14,008	14,468	28,924	28,201
Operating income		2,246	3,836	5,697	7,688
Identifiable assets at period end		48,064	58,570	48,064	58,570
Capital expenditures		957	317	1,212	802
Depreciation and amortization		300	288	620	541
Equity		24,320	39,482	24,320	39,482
Operating Segments | North Asia Segment
Segment Reporting Information [Line Items]
Total revenues		624,885	522,874	1,196,364	1,025,202
Net revenues	[1]	120,959	122,117	232,792	232,908
Operating income		58,093	61,721	111,445	116,939
Identifiable assets at period end		576,655	471,832	576,655	471,832
Capital expenditures		663	678	1,903	1,763
Depreciation and amortization		1,362	1,388	2,682	2,707
Equity		402,211	309,557	402,211	309,557
Operating Segments | South Asia Segment
Segment Reporting Information [Line Items]
Total revenues		163,106	158,216	315,777	300,440
Net revenues	[1]	38,228	46,257	76,223	85,775
Operating income		12,513	18,354	25,737	34,045
Identifiable assets at period end		129,002	118,352	129,002	118,352
Capital expenditures		409	351	782	1,006
Depreciation and amortization		556	543	1,087	1,055
Equity		117,077	78,668	117,077	78,668
Operating Segments | Europe Segment
Segment Reporting Information [Line Items]
Total revenues		269,197	239,979	509,976	472,237
Net revenues	[1]	80,896	77,639	156,854	152,180
Operating income		13,419	11,838	25,065	24,091
Identifiable assets at period end		437,628	378,859	437,628	378,859
Capital expenditures		10,501	2,140	15,579	4,259
Depreciation and amortization		1,227	1,188	2,398	2,286
Equity		135,726	133,387	135,726	133,387
Operating Segments | Middle East Africa And India Segment
Segment Reporting Information [Line Items]
Total revenues		101,798	85,832	198,748	174,155
Net revenues	[1]	30,286	28,975	60,017	59,382
Operating income		5,390	6,315	12,433	15,628
Identifiable assets at period end		207,191	225,877	207,191	225,877
Capital expenditures		429	570	768	1,813
Depreciation and amortization		480	489	940	940
Equity		124,628	141,315	124,628	141,315
Intersegment Eliminations
Segment Reporting Information [Line Items]
Total revenues		(59,680)	(63,146)	(115,035)	(122,138)
Net revenues	[1]	1,056	(14)	1,650	(11)
Operating income		(3)	(14)	(2)	(11)
Identifiable assets at period end		6,804	5,938	6,804	5,938
Equity		$ (35,244)	$ (31,418)	$ (35,244)	$ (31,418)

[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.