Share-Based Compensation Plans (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
Jun. 30, 2018	Jun. 30, 2017
Performance Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense, employees expensed in entirety	$ 10.6	$ 7.2

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration