Employee Benefit Plans - Fair Value of Pension Plan Assets (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 160.8	$ 153.4
Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3.5	5.2
Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	18.2	44.8
Domestic exchange-traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	33.0
International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	9.8	24.4
International and emerging markets exchange-traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	14.9
Exchange traded funds - U.S. Treasuries
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	24.7	16.3
Domestic corporate bonds and notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	40.9	45.0
Limited partnership investment in high-yield U.S. corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		6.4
Real estate partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		7.5
Foreign corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	5.4
Limited partnership interest in private equity fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.3	0.3
Exchange-traded global real estate fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	5.1
Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1.4	1.0
Exchange-traded commodity fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2.8	2.5
Other receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.8
Quoted Prices in Active Markets for Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	112.7	138.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	3.5	5.2
Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	18.2	44.8
Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic exchange-traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	33.0
Quoted Prices in Active Markets for Identical Assets (Level 1) | International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	9.7	24.4
Quoted Prices in Active Markets for Identical Assets (Level 1) | International and emerging markets exchange-traded funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	14.9
Quoted Prices in Active Markets for Identical Assets (Level 1) | Exchange traded funds - U.S. Treasuries
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	24.7	16.3
Quoted Prices in Active Markets for Identical Assets (Level 1) | Domestic corporate bonds and notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		45.0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Exchange-traded global real estate fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	5.1
Quoted Prices in Active Markets for Identical Assets (Level 1) | Exchange-traded commodity fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	2.8	2.5
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other receivables
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.8
Significant Other Observable Inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	46.4	0
Significant Other Observable Inputs (Level 2) | International
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.1
Significant Other Observable Inputs (Level 2) | Domestic corporate bonds and notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	40.9
Significant Other Observable Inputs (Level 2) | Foreign corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	5.4
Significant Un-observable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	1.7	15.2
Significant Un-observable Inputs (Level 3) | Limited partnership investment in high-yield U.S. corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		6.4
Significant Un-observable Inputs (Level 3) | Real estate partnership interests
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year		7.5
Significant Un-observable Inputs (Level 3) | Limited partnership interest in private equity fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	0.3	0.3
Significant Un-observable Inputs (Level 3) | Insurance contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets at end of year	$ 1.4	$ 1.0