Pension plans 2 (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Defined Benefit Plan, Change in Benefit Obligation and Fair Value of Plan Assets and Reconciliation of Funded Status [Abstract]
Accumulated benefit obligation at the end of the year	$ 709.9	$ 767.3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employear contributions	39.0	65.4
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current pension and other post-retirement liability	54.7	218.9
Deferred tax asset	55.6	120.9
Accumulated other comprehensive loss (income)	90.7	193.4
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Defined Benefit Plan, Plan Assets Percentage	90.00%
Defined Benefit Plan, Projected Benefit Obligation Percentage	89.00%
U.S. Pension Plans [Member]
Defined Benefit Plan, Change in Benefit Obligation and Fair Value of Plan Assets and Reconciliation of Funded Status [Abstract]
Benefit obligation at the beginning of the year	750.4	728.6
Service cost	11.2	11.7
Interest cost	29.5	30.1
Participant contributions	0	0
Plan amendments	0.5	3.4
Plan settlements	0	0
Plan curtailments	(32.6)	0
Benefits paid	(29.5)	(56.3)
Actuarial loss	(88.1)	32.9
Transfer in	0	0
Foreign currency exchange rates	0	0
Benefit obligation at the end of the year	641.4	750.4
Accumulated benefit obligation at the end of the year	641.4	703.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at the beginning of the year	555.3	481.4
Actual return on plan assets	65.2	68.6
Employear contributions	36.2	61.6
Plan settlements	0	0
Foreign currency exchange rates	0	0
Fair value of plan assets at the end of the year	627.2	555.3
Unfunded status at year end:	(14.2)	(195.1)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Prepaid benefit cost, non-current	23.2	0
Accrued benefit liability, current	(6.1)	(2.0)
Non-current pension and other post-retirement liability	(31.3)	(193.1)
Subtotal	(14.2)	(195.1)
Deferred tax asset	56.5	121.0
Accumulated other comprehensive loss (income)	89.4	191.6
Net amount related to pension plans	131.7	117.5
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Unrecognized net actuarial losses	139.7	304.9
Unrecognized net prior service costs	6.2	7.7
Unrecognized net transition costs	0	0
Tax benefit	(56.5)	(121.0)
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Net actuarial losses	11.0
Net prior service costs	1.5
Net transition costs	0
Total	12.5
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	37.4	750.4
Accumulated benefit obligation	37.4	703.0
Fair value of plan assets	0	555.2
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	37.4	750.4
Accumulated benefit obligation	37.4	703.0
Fair value of plan assets	0	555.2
Non-U.S. Pension Plans [Member]
Defined Benefit Plan, Change in Benefit Obligation and Fair Value of Plan Assets and Reconciliation of Funded Status [Abstract]
Benefit obligation at the beginning of the year	80.4	76.2
Service cost	2.8	3.0
Interest cost	3.0	3.6
Participant contributions	0.4	0.8
Plan amendments	0	0
Plan settlements	(4.2)	(2.9)
Plan curtailments	(0.9)	0
Benefits paid	(2.1)	(3.5)
Actuarial loss	1.9	(0.8)
Transfer in	0	1.4
Foreign currency exchange rates	2.1	2.6
Benefit obligation at the end of the year	83.4	80.4
Accumulated benefit obligation at the end of the year	68.5	64.3
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at the beginning of the year	63.3	58.7
Actual return on plan assets	5.5	4.3
Employear contributions	2.8	3.8
Plan settlements	(4.2)	(2.9)
Foreign currency exchange rates	1.5	2.1
Fair value of plan assets at the end of the year	67.2	63.3
Unfunded status at year end:	(16.2)	(17.1)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Prepaid benefit cost, non-current	0.4	0.9
Accrued benefit liability, current	(0.5)	(0.7)
Non-current pension and other post-retirement liability	(16.1)	(17.3)
Subtotal	(16.2)	(17.1)
Deferred tax asset	2.2	2.7
Accumulated other comprehensive loss (income)	6.1	6.3
Net amount related to pension plans	(7.9)	(8.1)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Unrecognized net actuarial losses	6.5	6.9
Unrecognized net prior service costs	0.4	0.5
Unrecognized net transition costs	1.4	1.6
Tax benefit	(2.2)	(2.7)
Pension and Other Postretirement Benefit Plans, Amounts that Will be Amortized from Accumulated Other Comprehensive Income (Loss) in Next Fiscal Year [Abstract]
Net actuarial losses	0.1
Net prior service costs	0.1
Net transition costs	0.2
Total	0.4
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	74.1	37.3
Accumulated benefit obligation	61.0	26.1
Fair value of plan assets	57.4	19.3
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	30.8	37.3
Accumulated benefit obligation	21.0	26.1
Fair value of plan assets	15.7	19.3
Pension Plans, Defined Benefit [Member]
Defined Benefit Plan, Change in Benefit Obligation and Fair Value of Plan Assets and Reconciliation of Funded Status [Abstract]
Service cost	14.0	14.7	13.5
Interest cost	32.5	33.7	35.2
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Defined Benefit Plan, Estimated Future Employer Contributions in Next Fiscal Year	$ 10.1