Loans - Credit Risk Profile by Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Residential Real Estate [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	$ 266,240	$ 261,912
Residential Real Estate [Member] | Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	264,338	259,869
Residential Real Estate [Member] | Non-Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	1,902	2,043
Consumer - Credit Card [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	3,031	3,199
Consumer - Credit Card [Member] | Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	3,031	3,174
Consumer - Credit Card [Member] | Non-Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		25
Consumer - Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,323	5,864
Consumer - Other [Member] | Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,319	5,854
Consumer - Other [Member] | Non-Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4	10
Consumer - Auto [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	33,857	32,184
Consumer - Auto [Member] | Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	33,847	32,173
Consumer - Auto [Member] | Non-Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	10	11
Student Loans - TERI [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,764	5,888
Student Loans - TERI [Member] | Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	5,726	5,869
Student Loans - TERI [Member] | Non-Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	38	19
Student Loans - Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,788	5,263
Student Loans - Other [Member] | Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total	4,788	5,083
Student Loans - Other [Member] | Non-Performing [Member]
Defined Benefit Plan Disclosure [Line Items]
Total		$ 180