Investment Securities - Sales of Securities and Gross Gains and Losses on Sales of Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Sale proceeds	$ 0	$ 0
Gross gains	0	0
Gross losses	$ 0	$ 0

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

No definition available.

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