Retirement Benefits - Obligations and Funded Status (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Benefit Plan, Funded Status of Plan [Abstract]
Net experience gains (losses) arising during the year	$ 253.6	$ 67.8	$ (68.2)
Reclassification adjustment for amortization of prior net experience loss included in net income	48.5	37.8	28.2
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax	0	19.3	0
Reclassification adjustment for amortization of prior service cost (credit) included in net income	3.5	2.7	1.2
US Plans [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	890.1	810.5
Service cost	0	0	0
Interest cost	46.2	46.5	47.7
Plan participant contributions	0	0
Plan settlements	0	0
Acquisition	0	0
Benefit paid	(39.7)	(38.0)
Actuarial (gains) losses	94.1	71.1
Foreign currency exchange effects	0	0
Benefit obligation at end of year	990.7	890.1	810.5
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	698.4	658.2
Return on assets - actual	26.0	77.4
Plan participant contributions	0	0
Employer contributions	0.7	0.8
Plan settlements	0	0
Acquisition	0	0
Benefit paid	(39.7)	(38.0)
Foreign currency effects	0	0
Fair value of plan assets at end of year	685.4	698.4	658.2
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(305.3)	(191.7)
Noncurrent asset	0	0
Current liability, included in accrued liabilities	13.2	1.4
Noncurrent liability	292.1	190.3
Net pension liability	305.3	191.7
Beginning of year - net gains and losses	(408.4)	(367.4)
Net experience gains (losses) arising during the year	(133.1)	(60.5)
Reclassification adjustment for amortization of prior net experience loss included in net income	28.2	19.5
End of year - net gains and losses	(513.3)	(408.4)	(367.4)
Beginning of year - net prior service cost (credit)	0	0
Reclassification adjustment for amortization of prior service cost (credit) included in net income	0	0
End of year - net prior service cost (credit)	0	0	0
Non-US Plans [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	289.6	223.4
Service cost	10.2	6.6	6.1
Interest cost	16.9	13.4	12.2
Plan participant contributions	3.5	2.9
Plan settlements	(2.8)	(0.5)
Acquisition	0	39.0
Benefit paid	(15.9)	(8.8)
Actuarial (gains) losses	15.9	15.7
Foreign currency exchange effects	(10.5)	(2.1)
Benefit obligation at end of year	306.9	289.6	223.4
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	218.6	188.9
Return on assets - actual	7.9	22.2
Plan participant contributions	3.5	2.9
Employer contributions	25.7	15.3
Plan settlements	(2.8)	(0.5)
Acquisition	0	0.6
Benefit paid	(15.9)	(8.8)
Foreign currency effects	(6.5)	(2.0)
Fair value of plan assets at end of year	230.5	218.6	188.9
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(76.4)	(71.0)
Noncurrent asset	(12.3)	(8.6)
Current liability, included in accrued liabilities	11.2	3.1
Noncurrent liability	77.5	76.5
Net pension liability	76.4	71.0
Beginning of year - net gains and losses	(19.6)	(17.4)
Net experience gains (losses) arising during the year	(20.0)	(4.1)
Reclassification adjustment for amortization of prior net experience loss included in net income	5.0	1.9
End of year - net gains and losses	(34.6)	(19.6)	(17.4)
Beginning of year - net prior service cost (credit)	(7.6)	(8.9)
Reclassification adjustment for amortization of prior service cost (credit) included in net income	1.5	1.3
End of year - net prior service cost (credit)	(6.1)	(7.6)	(8.9)
UMWA plans [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	474.3	465.5
Interest cost	24.0	27.1	25.8
Plan amendments	0	0
Benefit paid	(39.1)	(37.8)
Medicare subsidy received	3.4	3.2
Actuarial (gains) losses	67.0	16.3
Foreign currency exchange effects	0	0
Benefit obligation at end of year	529.6	474.3	465.5
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	310.2	308.0
Return on assets - actual	(5.1)	37.1
Employer contributions	0	0
Benefit paid	(40.5)	(38.1)
Medicare subsidy received	3.4	3.2
Fair value of plan assets at end of year	268.0	310.2	308.0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(261.6)	(164.1)
Current liability, included in accrued liabilities	0	0
Noncurrent liability	261.6	164.1
Net pension liability	261.6	164.1
Beginning of year - net gains and losses	(240.1)	(251.6)
Net experience gains (losses) arising during the year	97.6	4.5
Reclassification adjustment for amortization of prior net experience loss included in net income	14.7	16.0
End of year - net gains and losses	(323.0)	(240.1)	(251.6)
Beginning of year - net prior service cost (credit)	0	0
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax	0	0
Reclassification adjustment for amortization of prior service cost (credit) included in net income	0	0
End of year - net prior service cost (credit)	0	0	0
Black lung and other plans - postretirement medical [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	62.2	47.1
Interest cost	2.8	2.9
Plan amendments	0	19.3
Benefit paid	(7.0)	(5.9)
Medicare subsidy received	0	0
Actuarial (gains) losses	2.9	(1.3)
Foreign currency exchange effects	0	0.1
Benefit obligation at end of year	60.9	62.2
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	0	0
Return on assets - actual	0	0
Employer contributions	7.0	5.9
Benefit paid	(7.0)	(5.9)
Medicare subsidy received	0	0
Fair value of plan assets at end of year	0	0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(60.9)	(62.2)
Current liability, included in accrued liabilities	7.1	7.7
Noncurrent liability	53.8	54.5
Net pension liability	60.9	62.2
Beginning of year - net gains and losses	(7.6)	(9.3)
Net experience gains (losses) arising during the year	2.9	(1.3)
Reclassification adjustment for amortization of prior net experience loss included in net income	0.6	0.4
End of year - net gains and losses	(9.9)	(7.6)
Beginning of year - net prior service cost (credit)	(15.3)	2.6
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax	0	19.3
Reclassification adjustment for amortization of prior service cost (credit) included in net income	2.0	1.4
End of year - net prior service cost (credit)	(13.3)	(15.3)
Pension plan [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	1,179.7		1,033.9
Service cost	10.2	6.6	6.1
Interest cost	63.1	59.9	59.9
Plan participant contributions	3.5	2.9
Plan settlements	(2.8)	(0.5)
Acquisition	0	39.0
Benefit paid	(55.6)	(46.8)
Actuarial (gains) losses	110.0	86.8
Foreign currency exchange effects	(10.5)	(2.1)
Benefit obligation at end of year	1,297.6	1,179.7
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	917.0	847.1
Return on assets - actual	33.9	99.6
Plan participant contributions	3.5	2.9
Employer contributions	26.4	16.1
Plan settlements	(2.8)	(0.5)
Acquisition	0	0.6
Benefit paid	(55.6)	(46.8)
Foreign currency effects	(6.5)	(2.0)
Fair value of plan assets at end of year	915.9	917.0	847.1
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(381.7)	(262.7)
Noncurrent asset	(12.3)	(8.6)
Current liability, included in accrued liabilities	24.4	4.5
Noncurrent liability	369.6	266.8
Net pension liability	381.7	262.7
Beginning of year - net gains and losses	(428.0)	(384.8)
Net experience gains (losses) arising during the year	(153.1)	(64.6)
Reclassification adjustment for amortization of prior net experience loss included in net income	33.2	21.4
End of year - net gains and losses	(547.9)	(428.0)	(384.8)
Beginning of year - net prior service cost (credit)	(7.6)	(8.9)
Reclassification adjustment for amortization of prior service cost (credit) included in net income	1.5	1.3
End of year - net prior service cost (credit)	(6.1)	(7.6)	(8.9)
Retirement benefits other than pension [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	536.5	512.6
Interest cost	26.8	30.0	28.6
Plan amendments	0	19.3
Benefit paid	(46.1)	(43.7)
Medicare subsidy received	3.4	3.2
Actuarial (gains) losses	69.9	15.0
Foreign currency exchange effects	0	0.1
Benefit obligation at end of year	590.5	536.5	512.6
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	310.2	308.0
Return on assets - actual	(5.1)	37.1
Employer contributions	7.0	5.9
Benefit paid	(47.5)	(44.0)
Medicare subsidy received	3.4	3.2
Fair value of plan assets at end of year	268.0	310.2	308.0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(322.5)	(226.3)
Current liability, included in accrued liabilities	7.1	7.7
Noncurrent liability	315.4	218.6
Net pension liability	322.5	226.3
Beginning of year - net gains and losses	(247.7)	(260.9)
Net experience gains (losses) arising during the year	100.5	3.2
Reclassification adjustment for amortization of prior net experience loss included in net income	15.3	16.4
End of year - net gains and losses	(332.9)	(247.7)	(260.9)
Beginning of year - net prior service cost (credit)	(15.3)	2.6
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Prior Service Cost (Credit) Arising During Period, before Tax	0	19.3
Reclassification adjustment for amortization of prior service cost (credit) included in net income	2.0	1.4
End of year - net prior service cost (credit)	$ (13.3)	$ (15.3)	$ 2.6