Summary of Significant Accounting Policies - Impact of Adoption of ASUs on Condensed Consolidated Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Recurring services	$ 172.8	$ 160.9
Professional services and other	30.9	27.9
Total revenue	203.7	188.8
Selling, general, and administrative expense	66.2	54.9
Operating profit	27.4	28.0
Other income, net	1.6	(2.2)
Income tax expense	5.7	5.8
Net (loss) income attributable to Ceridian	$ 11.2	$ 0.6
Net loss per share attributable to Ceridian, basic and diluted		$ (0.07)
As Previously Reported [Member]
Revenue:
Recurring services		$ 167.0
Professional services and other		20.2
Total revenue		187.2
Selling, general, and administrative expense		56.8
Operating profit		24.5
Other income, net		(2.8)
Income tax expense		5.6
Net (loss) income attributable to Ceridian		$ (2.1)
Net loss per share attributable to Ceridian, basic and diluted		$ (0.11)
Accounting Standards Update 2014-09 [Member] | Adjustments [Member]
Revenue:
Recurring services		$ (6.1)
Professional services and other		7.7
Total revenue		1.6
Selling, general, and administrative expense		(1.3)
Operating profit		2.9
Income tax expense		0.2
Net (loss) income attributable to Ceridian		$ 2.7
Net loss per share attributable to Ceridian, basic and diluted		$ 0.04
Accounting Standards Update 2017-07 [Member] | Adjustments [Member]
Revenue:
Selling, general, and administrative expense		$ (0.6)
Operating profit		0.6
Other income, net		$ 0.6