Investment Securities - Scheduled Maturities of Investment Securities Available-for-Sale and Held-to-Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Available-for-Sale, Maturing within one year, Amortized Cost	$ 387
Available-for-Sale, Maturing after one to five years, Amortized Cost	8,173
Available-for-Sale, Maturing after five to ten years, Amortized Cost	100,395
Available-for-Sale, Maturing after ten years, Amortized Cost	68,524
Available-for-Sale, Amortized Cost	177,479	134,908
Available-for-Sale, Maturing within one year, Estimated Fair Value	388
Available-for-Sale, Maturing after one to five years, Estimated Fair Value	8,582
Available-for-Sale, Maturing after five to ten years, Estimated Fair Value	100,714
Available-for-Sale, Maturing after ten years, Estimated Fair Value	69,662
Available-for-Sale, Estimated Fair Value, Total	179,346	135,754
Held-to-Maturity, Maturing within one year, Amortized Cost
Held-to-Maturity, Maturing after one to five years, Amortized Cost
Held-to-Maturity, Maturing after five to ten years, Amortized Cost	14,362
Held-to-Maturity, Maturing after ten years, Amortized Cost	22,162
Held-to-Maturity, Amortized Cost	36,524	35,050
Held-to-Maturity, Maturing within one year, Estimated Fair Value
Held-to-Maturity, Maturing after one to five years, Estimated Fair Value
Held-to-Maturity, Maturing after five to ten years, Estimated Fair Value	14,320
Held-to-Maturity, Maturing after ten years, Estimated Fair Value	21,771
Held-to-Maturity, Estimated Fair Value, Total	$ 36,091