Credit Quality Assessment (Summary of Impaired Loans) (Detail) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Credit Quality Assessment [Abstract]
Impaired loans with a specific allowance	$ 10,587,000	$ 11,411,000
Impaired loans without a specific allowance	20,617,000	18,008,000
Total impaired loans	31,204,000	29,419,000
Allowance for loan and lease losses related to impaired loans	2,650,000	2,894,000
Allowance for loan and lease losses related to loans collectively evaluated	34,825,000	34,908,000
Total allowance for loan and lease losses	37,475,000	37,802,000
Average impaired loans for the period	30,312,000	34,331,000
Contractual interest income due on impaired loans during the period	698,000	2,339,000
Interest income on impaired loans recognized on a cash basis	190,000	773,000
Interest income on impaired loans recognized on an accrual basis	$ 66,000	$ 280,000