Employee Benefit Plans Change in Benefit Obligation and Plan Assets (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Mar. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Settlements		$ 131.1
Fair value of plan assets at beginning of year		713.4
Fair value of plan assets at end of year		643.7
Pension Contributions in Excess of Statutory Minimums	114.7
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Increase (decrease) in projected benefit obligation due to change in mortality assumptions		25.2
Service cost		3.5	3.4	3.1
Interest cost		36.1	33.8	35.1
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements		35.5	0	0
Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Increase (decrease) in projected benefit obligation due to change in mortality assumptions		19.0
Service cost		0.3	0.4	0.4
Interest cost		15.3	13.2	15.1
Settlements				(4.7)
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Settlements		0	0	(5.2)
Change in Benefit Obligation [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation at end of year		738.8	755.4	842.8
Service cost		3.5	3.4
Interest cost		36.1	33.8
Plan amendments		0	0
Actuarial loss (gain)		119.3	(92.6)
Change in GM Portion of OPEB Obligation		0	0
Participant contributions		0.4	0.4
Settlements		131.1	0
Benefit payments		(36.5)	(35.3)
Currency fluctuations		(8.3)	2.9
Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease)		(16.6)	(87.4)
Benefit payments		(36.5)	(35.3)
Change in Benefit Obligation [Member] \| Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Benefit obligation at end of year		654.7	577.9	601.3
Service cost		0.3	0.4
Interest cost		15.3	13.2
Plan amendments		0	(8.1)
Actuarial loss (gain)		41.2	(0.7)
Change in GM Portion of OPEB Obligation		31.8	(17.0)
Participant contributions		0	0
Settlements		0	0
Benefit payments		(11.8)	(11.2)
Currency fluctuations		0	0
Defined Benefit Plan, Benefit Obligation, Period Increase (Decrease)		76.8	(23.4)
Benefit payments		(11.8)	(11.2)
Change in Plan Assets [Member] \| Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Participant contributions		0.4	0.4
Benefit payments		(36.5)	(35.3)
Fair value of plan assets at beginning of year		713.4	695.4
Actual return on plan assets		77.2	49.2
Employer contributions		1.9	0.8
Benefit payments		(36.5)	(35.3)
Defined Benefit Plan, Settlements, Plan Assets		(104.2)	0
Currency fluctuations		(8.5)	2.9
Net change		(69.7)	18.0
Fair value of plan assets at end of year		643.7	713.4
Change in Plan Assets [Member] \| Other Postretirement Benefit Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Participant contributions		0	0
Benefit payments		(11.8)	(11.2)
Fair value of plan assets at beginning of year		0	0
Actual return on plan assets		0	0
Employer contributions		11.8	11.2
Benefit payments		(11.8)	(11.2)
Defined Benefit Plan, Settlements, Plan Assets		0	0
Currency fluctuations		0	0
Net change		0	0
Fair value of plan assets at end of year		$ 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.