Amortized Cost and Fair Value of Debt Securities by Contractual Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Amortized cost
Due in one year or less	$ 55
Due after one year through five years	8,099
Due after five years through ten years	27,759
Due after ten years	31,675
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Total	67,588
Mortgage-backed securities and CMO	43,515
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Total	111,103
Fair Value
Due in one year or less	55
Due after one year through five years	8,131
Due after five years through ten years	27,869
Due after ten years	31,541
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Total	67,596
Mortgage-backed securities and CMO	43,494
Available-for-sale Securities, Debt Securities, Total	111,090
Amortized cost
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	0
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Total	0
Mortgage-backed securities and CMO	11
Securities held to maturity, Amortized Cost	11	12
Fair Value
Due in one year or less	0
Due after one year through five years	0
Due after five years through ten years	0
Due after ten years	0
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Total	0
Mortgage-backed securities and CMO	11
Securities held to maturity, Fair Value	$ 11	$ 12