Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019	Jan. 01, 2018
Accounting Policies [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 15,345				$ 12,858				$ 15,345	$ 12,858	$ 9,247
Net foreign currency gains (losses)									(1,853)	(13,315)	7,955
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred contract costs	159,510				0				159,510	0			$ 135,000
Revenues	2,235,597	$ 2,090,947	$ 1,957,559	$ 1,854,262	1,901,371	$ 1,802,166	$ 1,672,279	$ 1,545,132	8,138,365	6,920,948	6,098,037
Costs and Expenses									7,341,802	6,220,688	5,427,874
Contract liabilities	$ 190,343				$ 0				190,343	0			165,000
Customs brokerage and other services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									2,614,679	$ 1,936,871	$ 1,727,196
Prospective Change in Presentation Gross vs Net | Customs brokerage and other services
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									225,000
Costs and Expenses									$ 225,000
Revenue Accounting Standards Update
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification													$ 22,000
Leases Accounting Standards Update | Scenario, Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating Lease, Right-of-Use Asset												$ 370,000
Operating Lease, Liability												$ 370,000