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Accounting Policies (Accounting Pronouncements) (Details) - USD ($) $ in Millions	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unfavorable impact on pre-tax operating results		$ (23.1)	$ 132.3
Accounting Standards Update 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Projected impact of new accounting principle on prior period operating income				$ 70.6
Forecast | Accounting Standards Update 2017-07 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Unfavorable impact on pre-tax operating results	$ 5.0

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(h)(1)(i))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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