Acquisitions - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2016	May 05, 2016	Dec. 31, 2015	Oct. 30, 2015	Oct. 08, 2015	Jun. 17, 2015	Feb. 04, 2015
Business Acquisition [Line Items]
Goodwill	$ 860,027,000		$ 858,532,000
Escrow deposits	206,212,000		$ 202,942,000
Acquired indefinite-lived intangible assets	61,100,000
Trade Names
Business Acquisition [Line Items]
Acquired indefinite-lived intangible assets	5,600,000
Customer Relationships
Business Acquisition [Line Items]
Acquired indefinite-lived intangible assets	$ 53,800,000
Average useful life, years	20 years
Noncompete Agreements
Business Acquisition [Line Items]
Acquired indefinite-lived intangible assets	$ 300,000
Average useful life, years	5 years
Customer Backlog
Business Acquisition [Line Items]
Acquired indefinite-lived intangible assets	$ 1,400,000
Acquisitions other than Faiveley
Business Acquisition [Line Items]
Escrow deposits	$ 37,600,000
Unitrac
Business Acquisition [Line Items]
Purchase price, net of cash acquired		$ 14,378,000
Goodwill		998,000
Goodwill tax deduction		$ 0
RMS
Business Acquisition [Line Items]
Purchase price, net of cash acquired				$ 18,710,000
Goodwill				8,847,000
Goodwill tax deduction				$ 0
Track IQ
Business Acquisition [Line Items]
Purchase price, net of cash acquired					$ 9,312,000
Goodwill					$ 6,649,000
MTC
Business Acquisition [Line Items]
Purchase price, net of cash acquired						$ 23,360,000
Goodwill						13,198,000
Goodwill tax deduction						$ 0
RCL
Business Acquisition [Line Items]
Purchase price, net of cash acquired							$ 78,011,000
Goodwill							$ 14,787,000