Business - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014 FinancialCenters Subsidiary	May 15, 2014 Branch	Sep. 30, 2014 Branch
Schedule Of Description Of Company [Line Items]
Number of inactive subsidiaries	1
Bank operated Business Financial Centers, number	40
Bank operated Commercial Banking Centers, number	6
Bank operated trust office locations, number	3
American Security Bank [Member]
Schedule Of Description Of Company [Line Items]
Total assets		$ 433
Number of bank branches		5
Electronic Branch [Member] | American Security Bank [Member]
Schedule Of Description Of Company [Line Items]
Number of bank branches		2
Number of banking vestibules closed			2