Premium on Debt Securities - Additional Information (Details) - Accounting Standards Update 2017-08 [Member] - USD ($)	Sep. 30, 2018	Jul. 01, 2018	Jun. 30, 2018
Cumulative-effect adjustment to retained earnings	$ (531,000)		$ (531,000)
Retained Earnings [Member]
Cumulative-effect adjustment to retained earnings	$ (531,000)	$ (531,000)	$ (531,000)

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

No definition available.

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