Amount of increase (decrease) in accumulated other comprehensive income.

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Amount of (increase) decrease to benefit obligation of defined benefit plan from remeasurement due to settlement. Excludes decrease to benefit obligation for settlement payment.

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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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 stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning of period			$ 2,672.5
Balance, end of period	$ 1,100.8	$ 2,985.0	1,100.8	$ 2,985.0
Postretirement benefit plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Decrease of benefit obligation for Remeasurement	174.5		174.5
Foreign Currency Translation Adjustment
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning of period			(4.3)
Reclassification from other comprehensive income to earnings			0.0
Current period change			1.8
Balance, end of period	(2.5)		(2.5)
Prior Service Credit (Cost) Associated with Postretirement Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning of period			35.9
Reclassification from other comprehensive income to earnings	(2.2)	(2.2)	(6.6)	(6.6)
Current period change			174.5
Balance, end of period	203.8		203.8
Accumulated other comprehensive income
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance, beginning of period	26.5	35.3	31.6	40.1
Reclassification from other comprehensive income to earnings			(6.6)
Current period change			176.3
Balance, end of period	$ 201.3	$ 31.8	$ 201.3	$ 31.8