Securities - Summary of Securities that had Unrealized Losses (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	$ 45,553		$ 39,274
Less than 12 Months, Aggregate Losses	338		337
Twelve Months or Longer, Fair Value	0		0
Twelve Months or Longer, Unrealized Losses	0		0
Total, Fair Value	45,553		39,274
Total, Unrealized Losses		(338)	(337)
U.S. Government agencies and corporations
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value			9,999
Less than 12 Months, Aggregate Losses			1
Twelve Months or Longer, Fair Value			0
Twelve Months or Longer, Unrealized Losses			0
Total, Fair Value			9,999
Total, Unrealized Losses			(1)
Mortgage backed securities
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	44,491		25,606
Less than 12 Months, Aggregate Losses		328	292
Twelve Months or Longer, Fair Value	0		0
Twelve Months or Longer, Unrealized Losses	0		0
Total, Fair Value	44,491		25,606
Total, Unrealized Losses		(328)	(292)
State and political subdivisions
Schedule of Available-for-sale Securities [Line Items]
Less than Twelve Months, Fair Value	1,062		3,669
Less than 12 Months, Aggregate Losses		10	44
Twelve Months or Longer, Fair Value	0		0
Twelve Months or Longer, Unrealized Losses	0		0
Total, Fair Value	1,062		3,669
Total, Unrealized Losses		$ (10)	$ (44)