Loans Receivable, Net and Allowance for Loan Losses - Schedule of Investment and Unpaid Principal Balances for Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Sep. 30, 2014
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 33,902		$ 33,902		$ 36,965
Unpaid Principal Balance	37,343		37,343		40,658
Associated Allowance	336		336		468
Average Recorded Investment	35,220	37,662	35,748	36,813
Interest Income Recognized	277	303	600	590
With no Specific Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	31,237		31,237		33,647
Unpaid Principal Balance	34,349		34,349		36,908
Average Recorded Investment	32,390	32,285	32,726	31,217
Interest Income Recognized	257	280	554	532
With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,665		2,665		3,318
Unpaid Principal Balance	2,994		2,994		3,750
Associated Allowance	336		336		468
Average Recorded Investment	2,830	5,377	3,022	5,596
Interest Income Recognized	20	23	46	58
Residential Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,167		12,167		13,638
Unpaid Principal Balance	14,252		14,252		16,222
Associated Allowance	280		280		334
Average Recorded Investment	12,962	13,098	13,193	13,090
Interest Income Recognized	83	117	206	208
Residential Real Estate Loans [Member] | With no Specific Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	9,715		9,715		11,030
Unpaid Principal Balance	11,523		11,523		13,225
Average Recorded Investment	10,551	9,630	10,740	9,855
Interest Income Recognized	64	94	163	150
Residential Real Estate Loans [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,452		2,452		2,608
Unpaid Principal Balance	2,729		2,729		2,997
Associated Allowance	280		280		334
Average Recorded Investment	2,411	3,468	2,453	3,235
Interest Income Recognized	19	23	43	58
Commercial Real Estate Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,785		20,785		22,244
Unpaid Principal Balance	22,039		22,039		23,105
Associated Allowance	4		4		84
Average Recorded Investment	21,357	23,040	21,459	22,396
Interest Income Recognized	190	183	384	374
Commercial Real Estate Loans [Member] | With no Specific Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,637		20,637		21,587
Unpaid Principal Balance	21,864		21,864		22,428
Average Recorded Investment	21,044	21,144	21,017	20,041
Interest Income Recognized	190	183	384	374
Commercial Real Estate Loans [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	148		148		657
Unpaid Principal Balance	175		175		677
Associated Allowance	4		4		84
Average Recorded Investment	313	1,896	442	2,355
Commercial Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	330		330		719
Unpaid Principal Balance	341		341		777
Average Recorded Investment	454	1,211	672	1,002
Interest Income Recognized	2	3	4	6
Commercial Loans [Member] | With no Specific Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	330		330		719
Unpaid Principal Balance	341		341		777
Average Recorded Investment	454	1,211	672	1,002
Interest Income Recognized	2	3	4	6
Home Equity Loans and Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	430		430		263
Unpaid Principal Balance	457		457		453
Associated Allowance	40		40		50
Average Recorded Investment	325	313	270	325
Interest Income Recognized			2	2
Home Equity Loans and Lines of Credit [Member] | With no Specific Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	389		389		210
Unpaid Principal Balance	391		391		377
Average Recorded Investment	286	300	244	319
Interest Income Recognized			2	2
Home Equity Loans and Lines of Credit [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	41		41		53
Unpaid Principal Balance	66		66		76
Associated Allowance	40		40		50
Average Recorded Investment	39	13	26	6
Auto Loans [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	190		190		101
Unpaid Principal Balance	254		254		101
Associated Allowance	12		12
Average Recorded Investment	122		154
Interest Income Recognized	2		4
Auto Loans [Member] | With no Specific Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	166		166		101
Unpaid Principal Balance	230		230		101
Average Recorded Investment	55		53
Interest Income Recognized	1		1
Auto Loans [Member] | With an Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	24		24
Unpaid Principal Balance	24		24
Associated Allowance	12		12
Average Recorded Investment	67		101
Interest Income Recognized	$ 1		$ 3