Employee Benefit Plans (Schedule of Underfunded Plan Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Pension Plan [Member]
Change in benefit obligation:
Benefit obligation, beginning balance	$ 42.2	$ 35.3
Service cost	1.7	1.4	1.3
Interest cost	1.8	1.9	1.7
Change in plan provisions	0	0
Benefits paid	(1.2)	(1.1)
Actuarial loss (gain)	(1.1)	4.7
Benefit obligation, ending balance	43.4	42.2	35.3
Change in fair value of plan assets:
Plan assets, beginning balance	0	0
Employer contribution	1.2	1.1
Benefits paid	(1.2)	(1.1)
Plan assets, ending balance	0	0	0
Underfunded status, end of year	(43.4)	(42.2)
Other Benefits [Member]
Change in benefit obligation:
Benefit obligation, beginning balance	24.6	14.7
Service cost	0.4	0.2	0.2
Interest cost	1.1	0.8	0.7
Change in plan provisions	0	1.3
Benefits paid	(0.9)	(0.6)
Actuarial loss (gain)	1.7	8.2
Benefit obligation, ending balance	26.9	24.6	14.7
Change in fair value of plan assets:
Plan assets, beginning balance	0	0
Employer contribution	0.9	0.6
Benefits paid	(0.9)	(0.6)
Plan assets, ending balance	0	0	0
Underfunded status, end of year	$ (26.9)	$ (24.6)