Pension and Other Post Retirement Benefits (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amounts recognized in balance sheet
Noncurrent assets	$ 78.4	$ 118.8
Noncurrent liabilities	75.6	84.2
U.S. qualified pension plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning Balance	909.9	746.4
Interest cost	42.5	41.9
Actuarial (gains)/losses	(135.0)	(127.2)
Benefits paid	7.1	5.6
Projected benefit obligation at the end of the period	1,080.3	909.9
Assumptions used to determine benefit obligations
Discount rate	4.69%	4.69%
Reconciliation of funded status to net amounts recognized
Funded status (deficit)	68.7	117.3
Net amounts recognized	68.7	117.3
Amounts recognized in balance sheet
Noncurrent assets	69.9	118.3
Noncurrent liabilities	1.2	1.0
Net amounts recognized	68.7	117.3
Amounts not yet reflected in net periodic benefit cost and included in AOCI
Accumulated gain (loss)	(221.5)	(149.5)
Accumulated other comprehensive income (AOCI)	(221.5)	(149.5)
Cumulative employer contributions in excess of net period benefit cost	290.2	266.8
Net amount recognized in the balance sheet	68.7	117.3
Information for pension plans with benefit obligations in excess of plan assets
Projected benefit obligation/APBO	1.2	1.0
Accumulated benefit obligations	1.2	1.0
U.S. qualified pension plan [Member] | Fair Value [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefits paid	7.1	5.5
Change in fair value of plan assets
Beginning balance	1,027.2	915.0
Actual return on assets	130.9	120.1
Expenses paid	2.0	2.4
Ending balance	1,149.0	1,027.2
U.S. qualified pension plan [Member] | Annual Expense [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Interest cost	42.5	41.9	39.5
Assumptions used to determine benefit obligations
Discount rate	4.69%	5.67%	6.15%
Expected return on plan assets	(71.6)	(63.8)	(61.0)
Amounts not yet reflected in net periodic benefit cost and included in AOCI
Accumulated gain (loss)	72.0	73.3	23.3
Accumulated other comprehensive income (AOCI)	72.0	73.3	23.3
U.K. pension plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning Balance	57.2	46.4
Service cost	7.4	6.0
Interest cost	2.8	2.5
Employee contributions	0.1	0.1
Actuarial (gains)/losses	0.2	(2.0)
Benefits paid	0.3	0.3
Rebates from UK Government	0.2	1.0
Exchange rate changes	3.1	(0.5)
Projected benefit obligation at the end of the period	70.3	57.2
Assumptions used to determine benefit obligations
Discount rate	4.70%	4.80%
Rate of compensation increase	3.10%	3.20%
Change in fair value of plan assets
Employee contributions	0.1	0.1
Rebates from UK Government	0.2	1.0
Reconciliation of funded status to net amounts recognized
Funded status (deficit)	8.5	0.5
Net amounts recognized	8.5	0.5
Amounts recognized in balance sheet
Noncurrent assets	8.5	0.5
Net amounts recognized	8.5	0.5
Amounts not yet reflected in net periodic benefit cost and included in AOCI
Accumulated gain (loss)	8.9	3.3
Accumulated other comprehensive income (AOCI)	8.9	3.3
Prepaid (unfunded accrrued) pension cost	(0.4)	(2.8)
Net amount recognized in the balance sheet	8.5	0.5
U.K. pension plan [Member] | Fair Value [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employee contributions	(0.1)	(0.1)
Benefits paid	0.3	0.3
Rebates from UK Government	0.9	1.7
Change in fair value of plan assets
Beginning balance	57.7	49.4
Actual return on assets	8.1	(0.4)
Company contributions	9.0	7.6
Employee contributions	(0.1)	(0.1)
Rebates from UK Government	0.9	1.7
Exchange rate	3.3	(0.4)
Ending balance	78.8	57.7
U.K. pension plan [Member] | Annual Expense [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	7.4	6.0	5.8
Interest cost	2.8	2.5	2.1
Assumptions used to determine benefit obligations
Discount rate	4.80%	5.30%	5.70%
Expected return on plan assets	(3.7)	(3.3)	(2.7)
Rate of compensation increase	3.20%	3.55%	4.20%
Amounts not yet reflected in net periodic benefit cost and included in AOCI
Accumulated gain (loss)	(4.9)	5.9	(1.1)
Accumulated other comprehensive income (AOCI)	(4.9)	5.9	(1.1)
Postretirement Medical Plan [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Beginning Balance	83.8	72.0
Service cost	3.3	3.0
Interest cost	3.5	3.7
Actuarial (gains)/losses	14.7	(5.3)
Benefits paid	0.2	0.2
Projected benefit obligation at the end of the period	75.7	83.8
Assumptions used to determine benefit obligations
Discount rate	2.94%	4.23%
Medical Assumptions
Trend assumed for the year	8.50%	8.97%
Ultimate trend rate	4.50%	4.50%
Year the ultimate trend rate is reached	2030	2030
Reconciliation of funded status to net amounts recognized
Funded status (deficit)	75.7	(83.8)
Net amounts recognized	75.7	(83.8)
Amounts recognized in balance sheet
Current liabilities	1.3	0.6
Noncurrent liabilities	74.4	83.2
Net amounts recognized	(75.7)	(83.8)
Amounts not yet reflected in net periodic benefit cost and included in AOCI
Accumulated gain (loss)	(4.4)	(20.4)
Accumulated other comprehensive income (AOCI)	(4.4)	(20.4)
Cumulative employer contributions in excess of net period benefit cost	(71.2)	(63.4)
Net amount recognized in the balance sheet	(75.6)	(83.8)
Information for pension plans with benefit obligations in excess of plan assets
Projected benefit obligation/APBO	75.7	83.8
Postretirement Medical Plan [Member] | Fair Value [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Employee contributions	0.2	0.2
Benefits paid	0.2	0.2
Change in fair value of plan assets
Employee contributions	0.2	0.2
Postretirement Medical Plan [Member] | Annual Expense [Member]
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Service cost	3.3	3.0	2.9
Interest cost	3.5	3.7	3.9
Assumptions used to determine benefit obligations
Discount rate	4.23%	5.33%	5.89%
Medical Assumptions
Trend assumed for the year	8.97%	9.47%	10.00%
Ultimate trend rate	4.50%	4.50%	4.50%
Year the ultimate trend rate is reached	2030	2030	2030
Amounts not yet reflected in net periodic benefit cost and included in AOCI
Accumulated gain (loss)	(15.9)	4.6	2.4
Accumulated other comprehensive income (AOCI)	$ (15.9)	$ 4.6	$ 2.4