Employee Benefit Plans (Accumulated Benefit Obligation) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Accumulated benefit obligation	$ 220.7	$ 242.8
Change in projected benefit obligation:
Projected benefit obligation at beginning of year	242.8	239.1
Interest cost	8.2	9.3	$ 10.1
Actuarial (gain) loss	(11.1)	11.7
Benefits paid	(19.2)	(17.3)
Projected benefit obligation at end of year	220.7	242.8	239.1
Change in plan assets:
Fair value of plan assets at beginning of year	256.9	245.3
Actual return on plan assets	(6.0)	30.6
Estimated expenses	(1.6)	(1.7)
Benefits paid	(19.2)	(17.3)
Fair value of plan assets at end of year	230.1	256.9	$ 245.3
Over funded status	9.4	14.1
Amounts recognized in the statement of financial position consist of:
Noncurrent assets	9.4	14.1
Net amount recognized	$ 9.4	$ 14.1
Weighted average assumptions used to determine benefit obligations:
Discount rate	4.21%	3.55%

Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of administration expense of defined benefit plan which decreases plan assets. Excludes plan administration expense paid by employer.

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Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans.

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Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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Amount of funded (unfunded) status of defined benefit plan, measured as difference between fair value of plan assets and benefit obligation. Includes, but is not limited to, overfunded (underfunded) status.

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Amount of cost recognized for passage of time related to defined benefit plan.

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Amount of payment to participant under defined benefit plan which decreases plan assets. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services.

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