Changes in Accumulated Other Comprehensive Income (Loss) - Narrative (Details) - USD ($) $ in Millions	5 Months Ended	6 Months Ended	12 Months Ended
May 31, 2019	Jun. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Abstract]
Amortization of actuarial losses, net of tax	$ 0.4	$ (19.0)	$ (0.2)	$ 0.8	$ 0.7
Amortization of actuarial losses, tax expense (benefit)	$ 0.1	$ 11.5	$ 0.1	0.2	0.4
Actuarial gains (losses), net of tax				(5.0)	1.3
Actuarial (losses) gains, tax expense (benefit)				$ 1.5	$ (0.1)

No definition available.

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Amount, after tax, of gain (loss) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, after tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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