Securities - Trading Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 4,358	$ 4,459
Corporate Equity Securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	2,998	3,117
Certificates of Deposit [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	253	408
International Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	257	287
Large Cap Growth Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	182	157
Large Cap Value Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	121	104
Real Estate Investment Trust Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	40	65
Corporate Notes and Bonds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	152	101
Mid Cap Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	81	26
Small Cap Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	81	26
U.S. Government Sponsored Entities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	53	58
Commodities Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	54	0
Money Market Mutual Funds [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Trading securities	$ 86	$ 110