Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Increase in pension liability	$ 0.7	$ 17.1	$ 0.7
Increase in net loss	0.4	10.5	11.0	1.3	6.5
Income tax effect attributable to pension and other postretirement benefit plans	0.3	6.6	6.9	0.8	4.1
Change in projected benefit obligation
Balance at beginning of the year		126.3	126.3	138.0
Service cost			0.7	0.5	0.6
Administration costs paid			(1.5)	(0.8)
Interest cost			5.9	5.4	5.7
Actuarial (gain) loss			32.6	(12.5)
Benefits paid			(5.1)	(4.3)
Balance at end of year	158.9		158.9	126.3	138.0
Change in fair value of plan assets
Balance at beginning of the year		103.7	103.7	115.8
Actual (loss) gain on assets			21.1	(7.7)
Employer contributions			0.7	0.7
Administration costs paid			(1.5)	(0.8)
Benefits paid			(5.1)	(4.3)
Fair value of plan assets at end of the year	118.9		118.9	103.7	115.8
Funded status at end of year	(40.0)		(40.0)	(22.6)
Amounts recognized in the consolidated balance sheet
Current liabilities	(40.0)		(40.0)	(0.6)
Noncurrent liabilities				(22.0)
Net amount recognized	(40.0)		(40.0)	(22.6)
Amounts recognized in accumulated other comprehensive income
Net actuarial loss recognized	58.9		58.9	42.2
Information for pension plans with an accumulated benefit obligation in excess of plan assets
Projected benefit obligation	158.9		158.9	126.3
Accumulated benefit obligation	158.9		158.9	126.3
Fair value of plan assets	118.9		118.9	103.7
Components of net periodic benefit cost
Service cost - administrative costs			0.7	0.5	0.6
Interest costs on benefits obligation			5.9	5.4	5.7
Expected return on assets			(6.3)	(6.8)	(6.9)
Net actuarial loss amortization			1.2	1.0	0.6
Net periodic benefit cost			1.5	0.1
Estimated amount that will be amortized from accumulated other comprehensive income into net periodic benefit cost over the next year
Net actuarial loss			$ 1.5
Pension Plan
Number of plans expects distribution			2
Minimum | SERP
Period to settle liabilities under SERP			12 months
Maximum | SERP
Period to settle liabilities under SERP			24 months