Schedule of Federal Reserve Bank Stock and Other Securities (Detail) (Federal Reserve Bank Stock and Other Securities [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Other Securities [Line Items]
Amortized Cost	$ 34,706	$ 33,438
Gross Unrealized Gains	19,845	17,044
Gross Unrealized Losses
Fair Value	54,551	50,482
Other securities - non-marketable [Member]
Schedule of Other Securities [Line Items]
Amortized Cost	18,427	17,139
Gross Unrealized Gains	2,460	432
Gross Unrealized Losses
Fair Value	20,887	17,571
Other securities - marketable [Member]
Schedule of Other Securities [Line Items]
Amortized Cost		20
Gross Unrealized Gains	17,385	16,612
Gross Unrealized Losses
Fair Value	17,385	16,632
Federal Reserve Bank Stock [Member]
Schedule of Other Securities [Line Items]
Amortized Cost	16,279	16,279
Gross Unrealized Gains
Gross Unrealized Losses
Fair Value	$ 16,279	$ 16,279