Gross Carrying Amounts and Accumulated Amortization of Intangible Assets and Goodwill (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Goodwill And Intangible Assets [Line Items]
Net Carrying Amount	$ 960	$ 1,330
Goodwill gross	84,171	84,171
Goodwill	84,171	84,171
Amortization of Intangible Assets
Goodwill And Intangible Assets [Line Items]
Gross Carrying Amount	18,339	18,339
Accumulated Amortization	(17,379)	(17,009)
Net Carrying Amount	960	1,330
Amortization of Intangible Assets | Core Deposits
Goodwill And Intangible Assets [Line Items]
Gross Carrying Amount	9,716	9,716
Accumulated Amortization	(9,607)	(9,352)
Net Carrying Amount	109	364
Weighted average useful life	1 month 6 days	3 months 18 days
Amortization of Intangible Assets | Other Intangible Assets
Goodwill And Intangible Assets [Line Items]
Gross Carrying Amount	8,623	8,623
Accumulated Amortization	(7,772)	(7,657)
Net Carrying Amount	$ 851	$ 966
Weighted average useful life	1 year 10 months 24 days	2 years 1 month 6 days