Investment Securities - Total Gross Realized Gains and Gross Realized Losses from Sale of Investment Securities (Detail) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Gross realized gains	$ 171,376	$ 633,244	$ 112,881
Gross realized losses	160,329	528,536	0
Net realized gains	$ 11,047	$ 104,708	$ 112,881

This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration