Defined Benefit Plans (Details) - Pension Plan - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,500.0	$ 1,305.0	$ 1,412.2
Projected benefit obligation	1,407.5	1,217.5	1,335.4
Net asset	92.5	87.5	76.8
Net periodic pension cost	8.6	7.4	4.0
Service cost	20.9	24.4	$ 22.2
Curtailment gain	1.4	$ 1.1
Contributions by employer	26.5
Contributions expected in next fiscal year	27.4
Quoted prices in active markets for identical assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,120.1
Significant other observable inputs (Level 2)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	113.3
Significant unobservable inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 266.6

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

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year.

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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 net periodic benefit cost (credit) for defined benefit plan.

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Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees.

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

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