Segment Information - Summary of Operations by Segment (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenue	$ 695.8	$ 708.4
Operating income (loss)	42.9	101.8
Services
Segment Reporting Information [Line Items]
Revenue	612.1	568.5
Operating income (loss)	15.2	17.1
Technology
Segment Reporting Information [Line Items]
Revenue	83.7	139.9
Operating income (loss)	29.4	82.0
Intersegment
Segment Reporting Information [Line Items]
Revenue	(2.4)	(10.0)
Intersegment | Services
Segment Reporting Information [Line Items]
Revenue	0.0	0.0
Intersegment | Technology
Segment Reporting Information [Line Items]
Revenue	2.4	10.0
Operating Segments
Segment Reporting Information [Line Items]
Operating income (loss)	44.6	99.1
Operating Segments | Services
Segment Reporting Information [Line Items]
Revenue	612.1	568.5
Operating Segments | Technology
Segment Reporting Information [Line Items]
Revenue	86.1	149.9
Corporate
Segment Reporting Information [Line Items]
Revenue	(2.4)	(10.0)
Operating income (loss)	$ (1.7)	$ 2.7