Fair Value Disclosures - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Assets:
Total available-for-sale securities	$ 304,302	$ 336,281
Fair Value Measured on Recurring Basis [Member]
Assets:
Total available-for-sale securities	304,302	336,281
Total assets	304,962	336,627
Liabilities:
Total liabilities	6,759	501
Fair Value Measured on Recurring Basis [Member] | U.S. Treasuries [Member]
Assets:
Total available-for-sale securities	4,790	4,708
Fair Value Measured on Recurring Basis [Member] | U.S. Government Corporations and Agencies [Member]
Assets:
Total available-for-sale securities	122,403	128,148
Fair Value Measured on Recurring Basis [Member] | State and Political Subdivisions [Member]
Assets:
Total available-for-sale securities	106,407	107,657
Fair Value Measured on Recurring Basis [Member] | Residential Mortgage-Backed Securities [Member]
Assets:
Total available-for-sale securities	13,553	35,480
Fair Value Measured on Recurring Basis [Member] | Collateralized Mortgage Obligations [Member]
Assets:
Total available-for-sale securities	6,475	7,201
Fair Value Measured on Recurring Basis [Member] | Corporate Bonds [Member]
Assets:
Total available-for-sale securities	42,975	33,840
Fair Value Measured on Recurring Basis [Member] | Money Market Mutual Funds [Member]
Assets:
Total available-for-sale securities	6,442	16,900
Fair Value Measured on Recurring Basis [Member] | Equity Securities [Member]
Assets:
Total available-for-sale securities	1,257	2,347
Fair Value Measured on Recurring Basis [Member] | Interest Rate Locks with Customers [Member]
Assets:
Interest rate locks with customers	660	321
Fair Value Measured on Recurring Basis [Member] | Contingent Consideration Liability [Member]
Liabilities:
Derivative liabilities	6,669	501
Fair Value Measured on Recurring Basis [Member] | Forward Loan Sale Commitments [Member]
Assets:
Interest rate locks with customers		25
Liabilities:
Derivative liabilities	90
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member]
Assets:
Total available-for-sale securities	12,489	23,955
Total assets	12,489	23,955
Liabilities:
Total liabilities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | U.S. Treasuries [Member]
Assets:
Total available-for-sale securities	4,790	4,708
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | U.S. Government Corporations and Agencies [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | State and Political Subdivisions [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Residential Mortgage-Backed Securities [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Collateralized Mortgage Obligations [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Corporate Bonds [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Money Market Mutual Funds [Member]
Assets:
Total available-for-sale securities	6,442	16,900
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Equity Securities [Member]
Assets:
Total available-for-sale securities	1,257	2,347
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Interest Rate Locks with Customers [Member]
Assets:
Interest rate locks with customers	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Contingent Consideration Liability [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 1 [Member] | Forward Loan Sale Commitments [Member]
Assets:
Interest rate locks with customers		0
Liabilities:
Derivative liabilities	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member]
Assets:
Total available-for-sale securities	291,813	312,326
Total assets	292,473	312,672
Liabilities:
Total liabilities	90	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | U.S. Treasuries [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | U.S. Government Corporations and Agencies [Member]
Assets:
Total available-for-sale securities	122,403	128,148
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | State and Political Subdivisions [Member]
Assets:
Total available-for-sale securities	106,407	107,657
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Residential Mortgage-Backed Securities [Member]
Assets:
Total available-for-sale securities	13,553	35,480
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Collateralized Mortgage Obligations [Member]
Assets:
Total available-for-sale securities	6,475	7,201
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Corporate Bonds [Member]
Assets:
Total available-for-sale securities	42,975	33,840
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Money Market Mutual Funds [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Equity Securities [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Interest Rate Locks with Customers [Member]
Assets:
Interest rate locks with customers	660	321
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Contingent Consideration Liability [Member]
Liabilities:
Derivative liabilities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 2 [Member] | Forward Loan Sale Commitments [Member]
Assets:
Interest rate locks with customers		25
Liabilities:
Derivative liabilities	90
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member]
Assets:
Total available-for-sale securities	0	0
Total assets	0	0
Liabilities:
Total liabilities	6,669	501
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | U.S. Treasuries [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | U.S. Government Corporations and Agencies [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | State and Political Subdivisions [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Residential Mortgage-Backed Securities [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Collateralized Mortgage Obligations [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Corporate Bonds [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Money Market Mutual Funds [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Equity Securities [Member]
Assets:
Total available-for-sale securities	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Interest Rate Locks with Customers [Member]
Assets:
Interest rate locks with customers	0	0
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Contingent Consideration Liability [Member]
Liabilities:
Derivative liabilities	6,669	501
Fair Value Measured on Recurring Basis [Member] | Level 3 [Member] | Forward Loan Sale Commitments [Member]
Assets:
Interest rate locks with customers		0
Liabilities:
Derivative liabilities	$ 0