Employee Benefit Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended			3 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Oct. 02, 2013
Non-qualified Plan Benefits
Defined Benefit Plan Disclosure [Line Items]
Estimated net loss, net of tax, that will be recognized in net periodic pension cost in next fiscal year	$ 0.2
Plans obligations	7.1			7.1
Discount rate	3.10%
Net periodic benefit cost	0.1	0.1	0.9
Net loss (net of taxes)	1.8			1.8
Unrecognized prior service credit (net of taxes)	(1.8)			(1.8)
Other Post-retirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets (percent)	0.00%	0.00%	0.00%
Estimated net prior service credit, net of tax, that will be recognized in net periodic pension cost in next fiscal year	0.2
Amortization period of unrecognized gains and losses	5 years
Plans obligations	(12.0)	(12.9)		(12.0)
Discount rate	4.10%	4.90%	4.10%
Net periodic benefit cost	1.0	(0.2)	0.4
Net loss (net of taxes)	0.5	1.1		0.5
Unrecognized prior service credit (net of taxes)	0	0		0
Current liabilities related to non-qualified plan and post-retirement benefits	0.8	0.9		0.8
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Expected return on plan assets (percent)	7.10%	8.00%	8.25%
Actual return on plan assets (percent)	8.12%
Pension contributions	5.7	0.1	2.6
Accumulated benefit obligation	203.2	173.6		203.2
Estimated net prior service credit, net of tax, that will be recognized in net periodic pension cost in next fiscal year	0.8
Estimated net loss, net of tax, that will be recognized in net periodic pension cost in next fiscal year	6.7
Plans obligations	(43.6)	(22.0)		(43.6)
Discount rate	4.00%	4.90%	4.10%
Net periodic benefit cost	3.4	6.2	7.3
Net loss (net of taxes)	47.3	33.2		47.3
Unrecognized prior service credit (net of taxes)	(3.4)	(3.9)		(3.4)
Current liabilities related to non-qualified plan and post-retirement benefits	0	0		0
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	(0.90%)			(0.90%)
Cash Balance Defined Benefit Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Description of interest credit rate basis	10-year U.S. Treasury rate
Non qualified and Post retirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Current liabilities related to non-qualified plan and post-retirement benefits	1.6			1.6
Defined Contribution 401k Plan
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percentage	3.00%
Company's matching contribution expense	0.7	0.7
Deferred Profit Sharing
Defined Benefit Plan Disclosure [Line Items]
Company's matching contribution expense	0.6	0.9
Minimum | Deferred Profit Sharing
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percentage	1.00%
Maximum | Deferred Profit Sharing
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution, percentage	5.00%
Materials & Construction
Defined Benefit Plan Disclosure [Line Items]
Company's matching contribution expense				$ 1.8
Materials & Construction | Defined Contribution 401k Plan
Defined Benefit Plan Disclosure [Line Items]
Maximum annual contribution per employee (in percent)					10.00%