Employee Benefit Plans Change in Benefit Obligation and Plan Assets (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	$ 611.3
Fair value of plan assets at end of year	702.2	$ 611.3
Pension Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	717.6	693.1
Service cost	3.6	2.9	$ 3.2
Interest cost	28.9	28.8	28.6
Plan amendments	0.5	0.0
Actuarial loss (gain)	28.1	54.8
Change in GM Portion of OPEB Obligation	0.0	0.0
Participant contributions	0.3	0.3
Settlements	(14.3)	0.0
Benefit payments	(40.8)	(38.1)
MPG acquisition / business combination	82.3	0.0
Currency fluctuations	17.8	(24.2)
Net change	106.4	24.5
Benefit obligation at end of year	824.0	717.6	693.1
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	611.3	612.8
Actual return on plan assets	74.9	61.7
Employer contributions	4.4	2.3
Participant contributions	0.3	0.3
Benefit payments	(40.8)	(38.1)
Settlements	(14.3)	0.0
MPG acquisition / business combination	49.9	0.0
Currency fluctuations	16.5	(27.7)
Net change	90.9	(1.5)
Fair value of plan assets at end of year	702.2	611.3	612.8
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation at beginning of year	571.7	588.4
Service cost	0.3	0.3	0.4
Interest cost	13.3	14.0	15.0
Plan amendments	0.0	0.0
Actuarial loss (gain)	22.6	(6.8)
Change in GM Portion of OPEB Obligation	16.5	(7.2)
Participant contributions	0.0	0.0
Settlements	0.0	0.0
Benefit payments	(12.5)	(17.0)
MPG acquisition / business combination	1.4	0.0
Currency fluctuations	0.0	0.0
Net change	41.6	(16.7)
Benefit obligation at end of year	613.3	571.7	588.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at beginning of year	0.0	0.0
Actual return on plan assets	0.0	0.0
Employer contributions	12.5	17.0
Participant contributions	0.0	0.0
Benefit payments	(12.5)	(17.0)
Settlements	0.0	0.0
MPG acquisition / business combination	0.0	0.0
Currency fluctuations	0.0	0.0
Net change	0.0	0.0
Fair value of plan assets at end of year	$ 0.0	$ 0.0	$ 0.0

Change in the amount estimated to be received from General Motors Company (GM) that relates to an agreement between us and GM to share proportionally in the cost of other postretirement employee benefits for eligible retirees based on the length of service an employee had with us and GM.

No definition available.