General (Narrative) (Details) - USD ($) $ in Millions		3 Months Ended
Jan. 01, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss)
Cumulative effect of new accounting principle in period of adoption	$ (151.2)
ASU 2014-09
New accounting pronouncement or change in accounting principle, effect of change on beginning retained earnings	3.0
ASU 2017-07
New accounting pronouncement or change in accounting principle, effect of change on operating results		$ 6.9
New accounting pronouncement or change in accounting principle, effect of change on other income		$ 6.9
ASU 2018-02
New accounting pronouncement or change in accounting principle, effect of change on beginning retained earnings	$ 151.0

Amount of cumulative effect of the change in accounting principle or new accounting pronouncement on retained earnings or other components of equity or net assets in the statement of financial position as of the beginning of the earliest period presented.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22580-107794

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22583-107794

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22499-107794

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant