Fair Value Measurements - Additional Information (Detail) $ in Thousands	3 Months Ended	6 Months Ended		12 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) Securities	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) Securities
Fair Value Measurements Disclosure [Line Items]
Percentage of securities using market-based information	99.90%	99.90%
Percentage of securities using model-based techniques	0.10%	0.10%
Minimum reserves for commercial loan	$ 500	$ 500
Number of securities transferred between hierarchy levels | Securities		0		0
Transfer of equity security to non-marketable equity securities	56
Impaired loans, carrying amount	68,308	$ 68,308		$ 69,450
Allocated allowance for loan losses	2,226	2,226
Fair value of allocated allowance	722	722
Estimated costs to sell	91	91
Provision for fair value measurements included in allowance for loan losses		1,046
Carrying amount of OREO	8,263	8,263
Written down of OREO		5,625
Fair value of OREO	6,336	6,336
Estimated cost to sell OREO		711
Loss from OREO included in earnings		$ 2,638
Short-term borrowings approximate fair value for amounts that mature, days, less than		90 days
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Measurements Disclosure [Line Items]
Impaired loans, carrying amount	2,857	$ 2,857
Allocated allowance for loan losses	722	722		1,705
Fair value of OREO	$ 6,336	6,336		$ 8,060
Assets Still Held [Member]
Fair Value Measurements Disclosure [Line Items]
Change in unrealized gains or losses included in earnings relating to assets still held		$ 0	$ 0