Employee Retirement Benefits - Changes in Projected Benefit Obligation, Changes in Plan Assets and Funded Status of Plan (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Pension
Change in Projected Benefit Obligations
Benefit obligations at beginning of year	$ 149.4	$ 143.0
Service cost	0.0	0.1	$ 0.1
Interest cost	6.1	5.8	5.6
Employee contributions	0.0	0.0
Plan settlements	(6.8)	(0.1)
Benefits paid	(0.3)	(3.7)
Net transfer	0.0	3.6
Actuarial loss	11.6	0.7
Benefit obligations at end of year	160.0	149.4	143.0
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	133.2	124.3
Actual return on plan assets	17.9	9.4
Company contributions	0.0	0.1
Employee contributions	0.0	0.0
Plan settlements	(6.8)	(0.1)
Benefits paid	(0.3)	(3.7)
Plan assets receivable from the Hertz Plan	(3.6)	3.2
Fair value of plan assets at end of year	140.4	133.2	124.3
Funded Status	(19.6)	(16.2)
Accumulated benefit obligations	160.0	149.4
Postretirement
Change in Projected Benefit Obligations
Benefit obligations at beginning of year	1.0	1.0
Service cost	0.0	0.0
Interest cost	0.0	0.0
Employee contributions	0.0	0.1
Plan settlements	0.0	0.0
Benefits paid	0.0	(0.1)
Net transfer	0.0	0.0
Actuarial loss	0.1	0.0
Benefit obligations at end of year	1.1	1.0	1.0
Change in Fair Value of Plan Assets
Fair value of plan assets at beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Company contributions	0.0	0.0
Employee contributions	0.0	0.1
Plan settlements	0.0	0.0
Benefits paid	0.0	(0.1)
Plan assets receivable from the Hertz Plan	0.0	0.0
Fair value of plan assets at end of year	0.0	0.0	$ 0.0
Funded Status	$ (1.1)	$ (1.0)