Interest-Bearing Time Deposits in Banks and Securities - Continuous Unrealized-Loss Position of Available-For-Sale and Held-To-Maturity Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Available For Sale And Held To Maturity Securities Continuous Unrealized Loss Position [Line Items]
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Fair Value	$ 71,271	$ 43,964
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	853	446
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Fair Value	3,574
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	42
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Fair Value	74,845	43,964
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Unrealized Loss	895	446
Obligations of U.S. government sponsored-enterprises and agencies [Member]
Schedule Of Available For Sale And Held To Maturity Securities Continuous Unrealized Loss Position [Line Items]
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Fair Value		3,114
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss		4
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Fair Value
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Fair Value		3,114
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Unrealized Loss		4
Obligations of state and political subdivisions [Member]
Schedule Of Available For Sale And Held To Maturity Securities Continuous Unrealized Loss Position [Line Items]
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Fair Value	36,480	9,595
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	129	98
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Fair Value
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Fair Value	36,480	9,595
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Unrealized Loss	129	98
Residential mortgage-backed securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities Continuous Unrealized Loss Position [Line Items]
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Fair Value	17,344	13,722
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	401	89
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Fair Value	3,574
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss	42
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Fair Value	20,918	13,722
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Unrealized Loss	443	89
Corporate Bonds And Other [Member]
Schedule Of Available For Sale And Held To Maturity Securities Continuous Unrealized Loss Position [Line Items]
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Fair Value	4,994	17,533
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	73	255
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Fair Value
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Fair Value	4,994	17,533
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Unrealized Loss	73	255
Commercial mortgage-backed securities [Member]
Schedule Of Available For Sale And Held To Maturity Securities Continuous Unrealized Loss Position [Line Items]
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Fair Value	12,453
Available-for-sale and held-to-maturity securities, continuous unrealized loss position Less than 12 Months, Unrealized Loss	250
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Fair Value
Available-for-sale and held-to-maturity securities, continuous unrealized loss position 12 Months or Longer, Unrealized Loss
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Fair Value	12,453
Available-for-sale and held-to-maturity securities, continuous unrealized loss position, Unrealized Loss	$ 250