Related Party Transactions (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
RSL and RSI \| RSL and RSI \| Service Agreement
Related Party Transaction [Line Items]
Expenses incurred under services agreements	$ 1.0	$ 1.0	$ 4.2	$ 2.1
RSL \| RSL \| Share-based Compensation, Expense Allocated to Company
Related Party Transaction [Line Items]
Expenses incurred under services agreements	$ 0.2	$ 0.3	$ 0.4	$ 0.5

Costs of sales and operating expenses for the period incurred from transactions with related parties.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

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