Investment Securities - Securities Held to Maturity by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Held-to-maturity Securities [Line Items]
Due in one year or less, Amortized cost	$ 13,572
Due after one year through five years, Amortized cost	50,356
Due after five years through ten years, Amortized cost	131,292
Due after ten years, Amortized cost	157,711
Amortized cost	357,602	357,500
Due in one year or less, Fair value	13,656
Due after one year through five years, Fair value	51,686
Due after five years through ten years, Fair value	134,548
Due after ten years, Fair value	157,490
Fair value	362,264	355,913
Mortgage-Backed Securities [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized cost	4,671	5,273
Fair value	$ 4,884	$ 5,520