Employee Benefits (Details 4) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended						12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 SERP's	Dec. 31, 2012 Defined Benefit Plans	Dec. 31, 2012 Postretirement Medical Plans Y item	Oct. 02, 2011 Postretirement Medical Plans	Dec. 31, 2012 Supplemental Bonus Plan	Dec. 31, 2011 Supplemental Bonus Plan	Dec. 31, 2010 Supplemental Bonus Plan
Effect of one-percentage-point change in assumed health care cost trend rates
Effect of 1% increase on total service and interest cost components	$ 0.1	$ 0.2
Effect of 1% decrease on total service and interest cost components	(0.1)	(0.2)
Effect of 1% increase on postretirement benefit obligation	0.6	1.0
Effect of 1% decrease on postretirement benefit obligation	(0.6)	(0.9)
Employee Benefits
Number of subsidiaries of entity					1
Maximum age limit for eligibility (in years)					65
Reduction to the benefit obligation due to amendment in terms of plan						10.1
Average remaining years of service to full eligibility					6
Summary of benefit payments under the Company's various defined benefit plans, which reflect expected future employee service, as appropriate, expected to be paid in the future periods
2013			1.4	2.7	0.7
2014			2.1	3.1	0.9
2015			2.1	3.4	0.9
2016			2.1	3.6	0.9
2017			2.6	3.8	1.0
2018-2022			13.5	21.7	5.7
Amounts in accumulated other comprehensive income that are expected to be recognized as components of net periodic benefit cost during 2013
Actuarial loss			1.2	1.5	0.5
Prior service (credit) cost			(0.4)	0.2	(1.7)
Total			0.8	1.7	(1.2)
General disclosures of the plan
Number of shares of the entity to be contributed to the plan as a result of acquisition							258,006
Number of shares equivalent to the cash liability associated with post-employment liability							121,965
Aggregate obligation to the plan acquired							7.4
(Income) expense from mark to market adjustments							$ 1.6	$ (0.2)	$ 1.1