Derivatives and Hedging Activities - Summary of Amounts Recorded in Balance Sheet Related to Cumulative Basis Adjustment for Fair Value Interest Rate Risk Hedges (Details) - USD ($) $ in Millions	Sep. 30, 2018	Jun. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Carrying amount of the hedged liabilities	$ 146.8	$ 147.1
Cumulative amount of fair value (gain) loss in the carrying amount of the hedged liabilities	$ (3.2)	$ (2.9)

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

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