Revenue - Costs to obtain or fulfill a contract (Details) - USD ($) $ in Millions	Mar. 31, 2019	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Costs to fulfill a contract	$ 13.0	$ 13.0
Amortization of deferred costs	$ 2.6	$ 1.3

Accumulated amortization of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs, deferred acquisition costs of insurance companies, or deferred leasing costs for real estate operations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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