Summary of Disaggregated Revenue by Business Line (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Revenue	$ 913,275	$ 933,224	$ 2,767,436	$ 2,665,300
Intermodal [Member]
Disaggregation Of Revenue [Line Items]
Revenue	539,484	582,878	1,618,407	1,615,453
Truck brokerage [Member]
Disaggregation Of Revenue [Line Items]
Revenue	109,543	122,059	334,211	357,013
Logistics [Member]
Disaggregation Of Revenue [Line Items]
Revenue	189,470	149,642	586,196	479,940
Dedicated [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 74,778	$ 78,645	$ 228,622	$ 212,894

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration