Retirement Benefits - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Compensation and Retirement Disclosure [Abstract]
Pension Contributions		$ 80.0
Postemployment Benefits, Period Expense	$ 0.1		$ 0.0	$ 0.3	$ 0.2
Defined Contribution Plan, Cost Recognized	$ 2.7		$ 2.4	$ 8.4	$ 7.0

Amount of contributions made by the employer to defined benefit plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(ii)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 60
-Section 35
-Paragraph 123
-Subparagraph B
-URI http://asc.fasb.org/extlink&oid=64937487&loc=d3e36068-114959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 30
-Section 35
-Paragraph 63
-Subparagraph B
-URI http://asc.fasb.org/extlink&oid=64937038&loc=d3e12551-114930

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(01)
-URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration