Retirement Benefits - Obligations and Funded Status (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Defined Benefit Plan, Funded Status of Plan [Abstract]
Noncurrent asset	$ (21.9)	$ (12.3)
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Net experience losses arising during the year	(47.0)	(253.6)	(67.8)
Reclassification adjustment for amortization of prior experience losses included in net income	74.3	48.5	37.8
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Prior service (cost) credit from plan amendments during the year	9.8	0	19.3
Reclassification adjustment for amortization of prior service cost included in net income	(4.0)	(3.5)	(2.7)
US Plans [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	990.7	890.1
Service cost	0	0	0
Interest cost	43.8	46.2	46.5
Participant contributions	0	0
Plan amendments	0	0
Curtailments	0	0
Settlements	(13.9)	0
Acquisition	0	0
Benefits paid	(42.3)	(39.7)
Actuarial (gains) losses	53.0	94.1
Foreign currency exchange effects	0	0
Benefit obligation at end of year	1,031.3	990.7	890.1
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	685.4	698.4
Return on assets - actual	89.9	26.0
Participant contributions	0	0
Employer contributions	37.2	0.7
Settlements	(13.9)	0
Acquisition	0	0
Benefits paid	(42.3)	(39.7)
Foreign currency effects	0	0
Fair value of plan assets at end of year	756.3	685.4	698.4
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(275.0)	(305.3)
Noncurrent asset	0	0
Current liability, included in accrued liabilities	0.9	13.2
Noncurrent liability	274.1	292.1
Net pension liability	275.0	305.3
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Beginning of year - net gains and losses	(513.3)	(408.4)
Net experience losses arising during the year	(23.1)	(133.1)
Reclassification adjustment for amortization of prior experience losses included in net income	44.5	28.2
End of year - net gains and losses	(491.9)	(513.3)	(408.4)
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Beginning of year - net prior service (cost) credit	0	0
Prior service (cost) credit from plan amendments during the year	0	0
Reclassification adjustment for amortization of prior service cost 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	306.9	289.6
Service cost	11.1	10.2	6.6
Interest cost	19.1	16.9	13.4
Participant contributions	3.5	3.5
Plan amendments	11.7	0
Curtailments	(0.4)	0
Settlements	(3.2)	(2.8)
Acquisition	0	0
Benefits paid	(22.0)	(15.9)
Actuarial (gains) losses	54.9	15.9
Foreign currency exchange effects	10.7	(10.5)
Benefit obligation at end of year	392.3	306.9	289.6
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	230.5	218.6
Return on assets - actual	34.7	7.9
Participant contributions	3.5	3.5
Employer contributions	32.8	25.7
Settlements	(3.2)	(2.8)
Acquisition	0	0
Benefits paid	(22.0)	(15.9)
Foreign currency effects	6.7	(6.5)
Fair value of plan assets at end of year	283.0	230.5	218.6
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(109.3)	(76.4)
Noncurrent asset	(21.9)	(12.3)
Current liability, included in accrued liabilities	7.5	11.2
Noncurrent liability	123.7	77.5
Net pension liability	109.3	76.4
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Beginning of year - net gains and losses	(34.6)	(19.6)
Net experience losses arising during the year	(32.4)	(20.0)
Reclassification adjustment for amortization of prior experience losses included in net income	7.3	5.0
End of year - net gains and losses	(59.7)	(34.6)	(19.6)
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Beginning of year - net prior service (cost) credit	(6.1)	(7.6)
Prior service (cost) credit from plan amendments during the year	(11.7)	0
Reclassification adjustment for amortization of prior service cost included in net income	2.0	1.5
End of year - net prior service (cost) credit	(15.8)	(6.1)	(7.6)
UMWA Plans Postretirement Medical [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	529.6	474.3
Service cost	0	0	0
Interest cost	22.3	24.0	27.1
Plan amendments	0	0
Benefits paid	(35.7)	(39.1)
Medicare subsidy received	3.2	3.4
Actuarial (gains) losses	5.9	67.0
Foreign currency exchange effects	0	0
Benefit obligation at end of year	525.3	529.6	474.3
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	268.0	310.2
Return on assets - actual	33.5	(5.1)
Employer contributions	0	0
Benefits paid	(36.0)	(40.5)
Medicare subsidy received	3.2	3.4
Fair value of plan assets at end of year	268.7	268.0	310.2
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(256.6)	(261.6)
Current liability, included in accrued liabilities	0	0
Noncurrent liability	256.6	261.6
Net pension liability	256.6	261.6
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Beginning of year - net gains and losses	(323.0)	(240.1)
Net experience losses arising during the year	(6.3)	97.6
Reclassification adjustment for amortization of prior experience losses included in net income	21.0	14.7
End of year - net gains and losses	(295.7)	(323.0)	(240.1)
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Beginning of year - net prior service (cost) credit	0	0
Prior service (cost) credit from plan amendments during the year	0	0
Reclassification adjustment for amortization of prior service cost included in net income	0	0
End of year - net prior service (cost) credit	0	0	0
Black Lung And Other Plans Postretirement [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	60.9	62.2
Service cost	0.6	0
Interest cost	2.8	2.8
Plan amendments	(1.9)	0
Benefits paid	(6.6)	(7.0)
Medicare subsidy received	0	0
Actuarial (gains) losses	(2.2)	2.9
Foreign currency exchange effects	(0.6)	0
Benefit obligation at end of year	53.0	60.9
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	6.6	7.0
Benefits paid	(6.6)	(7.0)
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	(53.0)	(60.9)
Current liability, included in accrued liabilities	5.0	7.1
Noncurrent liability	48.0	53.8
Net pension liability	53.0	60.9
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Beginning of year - net gains and losses	(9.9)	(7.6)
Net experience losses arising during the year	(2.2)	2.9
Reclassification adjustment for amortization of prior experience losses included in net income	1.5	0.6
End of year - net gains and losses	(6.2)	(9.9)
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Beginning of year - net prior service (cost) credit	(13.3)	(15.3)
Prior service (cost) credit from plan amendments during the year	1.9	0
Reclassification adjustment for amortization of prior service cost included in net income	2.0	2.0
End of year - net prior service (cost) credit	(9.4)	(13.3)
Pension plan [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	1,297.6		1,179.7
Service cost	11.1	10.2	6.6
Interest cost	62.9	63.1	59.9
Participant contributions	3.5	3.5
Plan amendments	11.7	0
Curtailments	(0.4)	0
Settlements	(17.1)	(2.8)
Acquisition	0	0
Benefits paid	(64.3)	(55.6)
Actuarial (gains) losses	107.9	110.0
Foreign currency exchange effects	10.7	(10.5)
Benefit obligation at end of year	1,423.6	1,297.6
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	915.9	917.0
Return on assets - actual	124.6	33.9
Participant contributions	3.5	3.5
Employer contributions	70.0	26.4
Settlements	(17.1)	(2.8)
Acquisition	0	0
Benefits paid	(64.3)	(55.6)
Foreign currency effects	6.7	(6.5)
Fair value of plan assets at end of year	1,039.3	915.9	917.0
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(384.3)	(381.7)
Noncurrent asset	(21.9)	(12.3)
Current liability, included in accrued liabilities	8.4	24.4
Noncurrent liability	397.8	369.6
Net pension liability	384.3	381.7
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Beginning of year - net gains and losses	(547.9)	(428.0)
Net experience losses arising during the year	(55.5)	(153.1)
Reclassification adjustment for amortization of prior experience losses included in net income	51.8	33.2
End of year - net gains and losses	(551.6)	(547.9)	(428.0)
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Beginning of year - net prior service (cost) credit	(6.1)	(7.6)
Prior service (cost) credit from plan amendments during the year	(11.7)	0
Reclassification adjustment for amortization of prior service cost included in net income	2.0	1.5
End of year - net prior service (cost) credit	(15.8)	(6.1)	(7.6)
Retirement benefits other than pension [Member]
Changes in the benefit obligation [Roll Forward]
Benefit obligation at beginning of year	590.5	536.5
Service cost	0.6	0	0
Interest cost	25.1	26.8	30.0
Plan amendments	(1.9)	0
Benefits paid	(42.3)	(46.1)
Medicare subsidy received	3.2	3.4
Actuarial (gains) losses	3.7	69.9
Foreign currency exchange effects	(0.6)	0
Benefit obligation at end of year	578.3	590.5	536.5
Changes in plan assets [Roll Forward]
Fair value of plan assets at beginning of year	268.0	310.2
Return on assets - actual	33.5	(5.1)
Employer contributions	6.6	7.0
Benefits paid	(42.6)	(47.5)
Medicare subsidy received	3.2	3.4
Fair value of plan assets at end of year	268.7	268.0	310.2
Defined Benefit Plan, Funded Status of Plan [Abstract]
Funded status	(309.6)	(322.5)
Current liability, included in accrued liabilities	5.0	7.1
Noncurrent liability	304.6	315.4
Net pension liability	309.6	322.5
Defined Benefit Plan Change In Net Actuarial Gains And Losses In Other Comprehensive Income [Roll Forward]
Beginning of year - net gains and losses	(332.9)	(247.7)
Net experience losses arising during the year	(8.5)	100.5
Reclassification adjustment for amortization of prior experience losses included in net income	22.5	15.3
End of year - net gains and losses	(301.9)	(332.9)	(247.7)
Defined Benefit Plan Change In Net Prior Service Cost Credit In Other Comprehensive Income [Roll Forward]
Beginning of year - net prior service (cost) credit	(13.3)	(15.3)
Prior service (cost) credit from plan amendments during the year	1.9	0
Reclassification adjustment for amortization of prior service cost included in net income	2.0
End of year - net prior service (cost) credit	$ (9.4)	$ (13.3)	$ (15.3)