Amortized Cost and Estimated Fair Values of Debt Securities Held-To-Maturity by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Amortized Cost
Due in one year or less	$ 1,690	$ 1,720
Due after one year through five years	1,564	3,249
Due after five years through ten years	145,655	139,033
Due after ten years	74,838	80,636
Total debt securities held-to-maturity	223,747	224,638
Estimated Fair Value
Due in one year or less	1,695	1,725
Due after one year through five years	1,569	3,269
Due after five years through ten years	144,499	135,074
Due after ten years	72,930	75,939
Total debt securities held-to-maturity	$ 220,693	$ 216,007