Goodwill and Other Intangible Assets - Additional Information (Detail)	12 Months Ended
Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Approximately weighted average remaining life of intangible assets	1 year 6 months
American Security Bank [Member]
Finite-Lived Intangible Assets [Line Items]
Approximately weighted average remaining life of intangible assets	1 year 4 months 24 days

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration