Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Employee Benefit Plans
Curtailment charges recorded to write-off previously unrecognized prior service costs		$ 1.5
Change in projected benefit obligation
Balance at beginning of the year	121.2	112.6
Service cost	0.6	5.3	4.6
Administration costs paid	(0.9)	(0.6)
Interest cost	5.7	6.0	5.7
Actuarial loss	15.6	13.6
Benefits paid	(4.2)	(3.2)
Curtailment adjustment		(12.5)
Balance at end of year	138.0	121.2	112.6
Change in fair value of plan assets
Balance at beginning of the year	108.4	90.3
Actual gain on assets	11.8	14.1
Employer contributions	0.7	7.8
Administration costs paid	(0.9)	(0.6)
Benefits paid	(4.2)	(3.2)
Fair value of plan assets at end of the year	115.8	108.4	90.3
Funded status at end of year	(22.2)	(12.8)
Amounts recognized in the consolidated balance sheet
Current liabilities	(0.6)	(0.2)
Noncurrent liabilities	(21.6)	(12.6)
Net amount recognized	(22.2)	(12.8)
Amounts recognized in accumulated other comprehensive income
Net actuarial loss recognized	41.2	31.1
Information for pension plans with an accumulated benefit obligation in excess of plan assets
Projected benefit obligation	138.0	13.6
Accumulated benefit obligation	138.0	13.6
Fair value of plan assets	115.8
Information for pension plans with plan assets in excess of accumulated benefit obligation
Projected benefit obligation		107.6
Accumulated benefit obligation		107.6
Fair value of plan assets		108.4
Components of net periodic benefit cost
Service cost-benefits earned	0.6	5.3	4.6
Interest costs on benefits obligation	5.7	6.0	5.7
Expected return on assets	(6.9)	(7.5)	(6.0)
Prior service cost amortization		0.3	0.3
Net actuarial loss amortization	0.6	2.7	2.3
Curtailment charge		1.5
Net periodic benefit cost		8.3	6.9
Estimated amount that will be amortized from accumulated other comprehensive income into net periodic benefit cost over the next year
Net actuarial loss	$ 1.0