Investment Securities (Available For Sale Securities With Gross Unrealized Losses By Investment Category And Length Of Time Individual Securities Have Been In Continuous Loss Position) (Detail) Number in Thousands, $ in Thousands	Dec. 31, 2018 USD ($) Number	Sep. 30, 2018 USD ($) Number
Investments, Unrealized Loss Position [Line Items]
Securities available for sale, Continuous loss position less than twelve months, Number of Investment Positions | Number	44	112
Securities available for sale, Continuous loss position more than twelve months, Number of Investment Positions | Number	58	30
Securities available for sale, Number of Investment Positions | Number	102	142
Securities available for sale, Continuous loss position less than twelve months, Fair Value	$ 25,815	$ 61,536
Securities available for sale, Continuous loss position more than twelve months, Fair Value	37,593	23,924
Securities available for sale, Continuous loss position	63,408	85,460
Securities available for sale, Continuous loss position less than twelve months, Gross Unrealized Losses	217	1,311
Securities available for sale, Continuous loss position more than twelve months, Gross Unrealized Losses	1,114	1,003
Securities available for sale, Continuous loss position, Gross Unrealized Losses	$ 1,331	$ 2,314
Agency Mortgage-Backed
Investments, Unrealized Loss Position [Line Items]
Securities available for sale, Continuous loss position less than twelve months, Number of Investment Positions | Number	5	15
Securities available for sale, Continuous loss position more than twelve months, Number of Investment Positions | Number	18	11
Securities available for sale, Continuous loss position less than twelve months, Fair Value	$ 6,097	$ 14,814
Securities available for sale, Continuous loss position more than twelve months, Fair Value	12,293	9,283
Securities available for sale, Continuous loss position less than twelve months, Gross Unrealized Losses	46	313
Securities available for sale, Continuous loss position more than twelve months, Gross Unrealized Losses	$ 370	$ 333
Agency CMO
Investments, Unrealized Loss Position [Line Items]
Securities available for sale, Continuous loss position less than twelve months, Number of Investment Positions | Number	1	4
Securities available for sale, Continuous loss position more than twelve months, Number of Investment Positions | Number	12	9
Securities available for sale, Continuous loss position less than twelve months, Fair Value	$ 119	$ 2,560
Securities available for sale, Continuous loss position more than twelve months, Fair Value	10,000	7,881
Securities available for sale, Continuous loss position less than twelve months, Gross Unrealized Losses	6	54
Securities available for sale, Continuous loss position more than twelve months, Gross Unrealized Losses	$ 227	$ 259
Municipal bonds
Investments, Unrealized Loss Position [Line Items]
Securities available for sale, Continuous loss position less than twelve months, Number of Investment Positions | Number	38	93
Securities available for sale, Continuous loss position more than twelve months, Number of Investment Positions | Number	26	8
Securities available for sale, Continuous loss position less than twelve months, Fair Value	$ 19,599	$ 44,162
Securities available for sale, Continuous loss position more than twelve months, Fair Value	14,669	6,106
Securities available for sale, Continuous loss position less than twelve months, Gross Unrealized Losses	165	944
Securities available for sale, Continuous loss position more than twelve months, Gross Unrealized Losses	$ 508	$ 401
Privately-issued CMO
Investments, Unrealized Loss Position [Line Items]
Securities available for sale, Continuous loss position more than twelve months, Number of Investment Positions | Number	1	1
Securities available for sale, Continuous loss position more than twelve months, Fair Value	$ 36	$ 37
Securities available for sale, Continuous loss position more than twelve months, Gross Unrealized Losses	$ 4	$ 3
SBA certificates
Investments, Unrealized Loss Position [Line Items]
Securities available for sale, Continuous loss position more than twelve months, Number of Investment Positions | Number	1	1
Securities available for sale, Continuous loss position more than twelve months, Fair Value	$ 595	$ 617
Securities available for sale, Continuous loss position more than twelve months, Gross Unrealized Losses	$ 5	$ 7