Employee Benefit Plans (Fair Values of Pension Plan Assets by Category) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 292.5	$ 293.0
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.3	3.8
Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	287.2	289.2
Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and Cash Equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.3	3.8
Cash and Cash Equivalents [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.3	3.8
Cash and Cash Equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and Cash Equivalents [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. Equity [Member] | Commingled Pools / Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69.5	69.7
U.S. Equity [Member] | Commingled Pools / Collective Trusts [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. Equity [Member] | Commingled Pools / Collective Trusts [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69.5	69.7
U.S. Equity [Member] | Commingled Pools / Collective Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International Equity [Member] | Commingled Pools / Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.6	45.5
International Equity [Member] | Commingled Pools / Collective Trusts [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International Equity [Member] | Commingled Pools / Collective Trusts [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	47.6	45.5
International Equity [Member] | Commingled Pools / Collective Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International Equity [Member] | Trust for Benefit of Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.7	4.7
International Equity [Member] | Trust for Benefit of Employees [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International Equity [Member] | Trust for Benefit of Employees [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.7	4.7
International Equity [Member] | Trust for Benefit of Employees [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International Equity [Member] | Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.5	11.0
International Equity [Member] | Pension Fund [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International Equity [Member] | Pension Fund [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.5	11.0
International Equity [Member] | Pension Fund [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income [Member] | Commingled Pools / Collective Trusts [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134.9	138.1
Fixed Income [Member] | Commingled Pools / Collective Trusts [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income [Member] | Commingled Pools / Collective Trusts [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	134.9	138.1
Fixed Income [Member] | Commingled Pools / Collective Trusts [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income [Member] | Trust for Benefit of Employees [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.9	12.1
Fixed Income [Member] | Trust for Benefit of Employees [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income [Member] | Trust for Benefit of Employees [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.9	12.1
Fixed Income [Member] | Trust for Benefit of Employees [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income [Member] | Pension Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.1	8.1
Fixed Income [Member] | Pension Fund [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Fixed Income [Member] | Pension Fund [Member] | Significant Other Observable Inputs (Level 2) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.1	8.1
Fixed Income [Member] | Pension Fund [Member] | Significant Unobservable Inputs (Level 3) [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ 0.0