Pension plans 2 (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	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	$ 767.3	$ 741.5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Employear contributions	65.4	19.7
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Non-current pension and other post-retirement liability	218.9	243.4
Deferred tax asset	120.9	130.1
Accumulated other comprehensive loss (income)	193.4	219.6
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	41.0
Defined Benefit Plan, Plan Assets Percentage	90.00%
Defined Benefit Plan, Projected Benefit Obligation Percentage	90.00%
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	728.6	612.4
Service cost	11.7	10.5
Interest cost	30.1	31.4
Participant contributions	0	0
Plan amendments	3.4	0.5
Plan settlements	0	0
Plan curtailments	0	0
Benefits paid	(56.3)	(27.0)
Actuarial loss	32.9	100.8
Transfer in	0	0
Foreign currency exchange rates	0	0
Benefit obligation at the end of the year	750.4	728.6
Accumulated benefit obligation at the end of the year	703.0	681.5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at the beginning of the year	481.4	476.9
Actual return on plan assets	68.6	15.1
Employear contributions	61.6	16.4
Plan settlements	0	0
Acquisition	0	0
Foreign currency exchange rates	0	0
Fair value of plan assets at the end of the year	555.3	481.4
Unfunded status at year end:	(195.1)	(247.2)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Prepaid benefit cost, non-current	0	0
Accrued benefit liability, current	(2.0)	(29.9)
Non-current pension and other post-retirement liability	(193.1)	(217.3)
Subtotal	(195.1)	(247.2)
Deferred tax asset	121.0	129.1
Accumulated other comprehensive loss (income)	191.6	218.0
Net amount related to pension plans	117.5	99.9
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Unrecognized net actuarial losses	304.9	341.3
Unrecognized net prior service costs	7.7	5.8
Unrecognized net transition costs	0	0
Tax benefit	(121.0)	(129.1)
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	26.0
Net prior service costs	1.7
Net transition costs	0
Total	27.7
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	750.4	728.6
Accumulated benefit obligation	703.0	681.5
Fair value of plan assets	555.2	481.4
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	750.4	728.6
Accumulated benefit obligation	703.0	681.5
Fair value of plan assets	555.2	481.4
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	76.2	69.6
Service cost	3.0	3.0
Interest cost	3.6	3.9
Participant contributions	0.8	0.6
Plan amendments	0	0
Plan settlements	(2.9)	(3.6)
Plan curtailments	0	(3.0)
Benefits paid	(3.5)	(3.5)
Actuarial loss	(0.8)	4.0
Transfer in	1.4	7.2
Foreign currency exchange rates	2.6	(2.0)
Benefit obligation at the end of the year	80.4	76.2
Accumulated benefit obligation at the end of the year	64.3	60.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets at the beginning of the year	58.7	52.3
Actual return on plan assets	4.3	1.9
Employear contributions	3.8	3.3
Plan settlements	(2.9)	0
Acquisition		5.5
Foreign currency exchange rates	2.1	(1.4)
Fair value of plan assets at the end of the year	63.3	58.7
Unfunded status at year end:	(17.1)	(17.5)
Defined Benefit Plan, Amounts Recognized in Balance Sheet [Abstract]
Prepaid benefit cost, non-current	0.9	0.2
Accrued benefit liability, current	(0.7)	(0.3)
Non-current pension and other post-retirement liability	(17.3)	(17.4)
Subtotal	(17.1)	(17.5)
Deferred tax asset	2.7	4.1
Accumulated other comprehensive loss (income)	6.3	6.9
Net amount related to pension plans	(8.1)	(6.5)
Pension and Other Postretirement Benefit Plans, Accumulated Other Comprehensive Income (Loss), before Tax [Abstract]
Unrecognized net actuarial losses	6.9	8.6
Unrecognized net prior service costs	0.5	0.6
Unrecognized net transition costs	1.6	1.8
Tax benefit	(2.7)	(4.1)
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	0.3
Net prior service costs	0.1
Net transition costs	0.2
Total	0.6
Defined Benefit Plan, Plans with Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	37.3	76.2
Accumulated benefit obligation	26.1	60.0
Fair value of plan assets	19.3	58.6
Defined Benefit Plan, Pension Plans with Accumulated Benefit Obligations in Excess of Plan Assets [Abstract]
Projected benefit obligation	37.3	34.8
Accumulated benefit obligation	26.1	25.3
Fair value of plan assets	$ 19.3	$ 21.2