Segment Information - Customer Revenue by Classes of Similar Products or Services (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from External Customer [Line Items]
Revenues	$ 438.8	$ 569.4	$ 954.2	$ 1,123.9
Services
Revenue from External Customer [Line Items]
Revenues	396.0	481.0	821.9	955.0
Technology
Revenue from External Customer [Line Items]
Revenues	42.8	88.4	132.3	168.9
Cloud & infrastructure services | Services
Revenue from External Customer [Line Items]
Revenues	275.7	320.5	570.9	642.2
Application services | Services
Revenue from External Customer [Line Items]
Revenues	82.4	95.1	167.5	185.6
Business process outsourcing services | Services
Revenue from External Customer [Line Items]
Revenues	$ 37.9	$ 65.4	$ 83.5	$ 127.2