Securities - Trading Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 4,502	$ 4,505
Corporate Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	3,034	3,044
Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	1,000	997
Certificates of Deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	256	253
Corporate Notes and Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	157	157
U.S. Government Sponsored Entities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 55	$ 54