Acquisitions Acquisitions - Acquired Entities (Details)							12 Months Ended
	Oct. 31, 2017	Aug. 14, 2017	Jul. 18, 2017 USD ($) employee vehicle branch	Jun. 29, 2017	Apr. 19, 2017	Mar. 14, 2017	Dec. 31, 2017 USD ($) employee acquisition	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill							$ 453,700,000	$ 186,200,000	$ 185,300,000
Other Acquisitions
Business Acquisition [Line Items]
Entity Number of Employees | employee							1,700
Number of acquired operations | acquisition							5
Goodwill increase							$ 14,000,000
Intangible asset decrease							11,000,000
Noncurrent liability increase							6,000,000
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Purchase consideration - cash paid							160,400,000
Indemnification asset							(4,000,000)
Fair value of future payments to sellers							3,900,000
Fair value of purchase consideration							160,300,000
Cash							7,400,000
Accounts receivables							20,100,000
Property and Equipment, net							13,200,000
Intangible assets							39,600,000
Goodwill							118,900,000
Other noncurrent assets							5,000,000
Current liabilities							(24,200,000)
Noncurrent liabilities							(19,700,000)
Fair value of net assets acquired							160,300,000
Maco
Business Acquisition [Line Items]
Acquisition date			Jul. 18, 2017
Percentage of shares acquired			100.00%
Scheduled Installments Period			2 years
Potential undiscounted amount minimum			$ 0
Potential undiscounted amount maximum			$ 30,300,000.0				$ 30,300,000
Revenue Multiple			2.5
Entity Number of Employees | employee			1,450
Entity Number Of Branches | branch			4
Entity Number Of Armored Vehicles | vehicle			150
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Purchase consideration - cash paid			$ 173,300,000
Fair value of future payments to sellers			2,500,000
Contingent consideration			28,700,000
Fair value of purchase consideration			204,500,000
Cash			10,300,000
Accounts receivables			16,600,000
Other current assets			600,000
Property and Equipment, net			2,400,000
Intangible assets			60,200,000
Goodwill			147,600,000
Other noncurrent assets			100,000
Current liabilities			(11,800,000)
Noncurrent liabilities			(21,500,000)
Fair value of net assets acquired			$ 204,500,000
AATI
Business Acquisition [Line Items]
Acquisition date						Mar. 14, 2017
Percentage of shares acquired						100.00%
Pag Facil
Business Acquisition [Line Items]
Acquisition date					Apr. 19, 2017
Percentage of shares acquired					100.00%
LGS
Business Acquisition [Line Items]
Acquisition date				Jun. 29, 2017
Percentage of shares acquired				100.00%
Maco Litoral
Business Acquisition [Line Items]
Acquisition date		Aug. 14, 2017
Percentage of shares acquired		100.00%
Temis
Business Acquisition [Line Items]
Acquisition date	Oct. 31, 2017
Percentage of shares acquired	100.00%