Employee Benefit Plans US Changes in Assets measured at fair value using significant unobservable inputs (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Level 3 Transfers Into	$ 0
Fair Value, Inputs, Level 3 | Pension Benefits, U.S. Plans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Assets Measured with Unobservable Inputs, Beginning Balance	103.7	84.8
Defined Benefit Plan, Actual Return on Plan Assets Still Held	9.7	7.5
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	2.6	1.1
Purchases	38.8	15.4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(32.7)	(5.1)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	122.1	103.7
Private Equity Direct Investments | Fair Value, Inputs, Level 3 | Pension Benefits, U.S. Plans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Assets Measured with Unobservable Inputs, Beginning Balance	7.2	0
Defined Benefit Plan, Actual Return on Plan Assets Still Held	1.7	0.3
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	0.1	0
Purchases	9.0	8.4
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(0.8)	(1.5)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	17.2	7.2
Private Equity Funds | Fair Value, Inputs, Level 3 | Pension Benefits, U.S. Plans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Assets Measured with Unobservable Inputs, Beginning Balance	29.6	28.7
Defined Benefit Plan, Actual Return on Plan Assets Still Held	4.8	0.9
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	2.6	1.1
Purchases	3.9	2.1
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(6.0)	(3.2)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	34.9	29.6
Hedge Funds | Fair Value, Inputs, Level 3 | Pension Benefits, U.S. Plans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation
Assets Measured with Unobservable Inputs, Beginning Balance	66.9	56.1
Defined Benefit Plan, Actual Return on Plan Assets Still Held	3.2	6.3
Defined Benefit Plan, Actual Return on Plan Assets Sold During Period	(0.1)	0
Purchases	25.9	4.9
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales	(25.9)	(0.4)
Level 3 Transfers Into	0	0
Level 3 Transfers Out of	0	0
Assets Measured with Unobservable Inputs, Ending Balance	$ 70.0	$ 66.9