Consolidated Statements of Comprehensive Income (Loss) (Parenthetical) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Nov. 30, 2015
Statement of Comprehensive Income [Abstract]
Actuarial (losses) gains, income tax	$ 1.7	$ 24.5	$ 23.2	$ 31.3
Actuarial gains (losses), tax expense (benefit)	4.6	2.9	4.8	36.9
Amortization of prior service credits, income tax	$ 0.0	$ 0.0	$ 0.4	$ 0.4

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.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=84228862&loc=d3e640-108580

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Amount of tax (expense) benefit of reclassification adjustment from accumulated other comprehensive (income) loss for prior service cost (credit) of defined benefit plan.

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

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