Investment Securities (Gross Losses on Sale of Investment Securities) (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Realized gains	$ 9	$ 257
Realized losses	(4)	(15)
Gross realized losses on securities	$ 5	$ 242

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