Loans and Allowance for Loan Losses - Company's Impaired Loans (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Financing Receivable, Impaired [Line Items]
Recorded Investment	$ 19,057	$ 27,025
Unpaid Principal Balance	20,685	28,887
Related Allowance	2,692	4,516
Average Recorded Investment	20,019	34,629
Interest Income Recognized	605	755
With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,780	9,590
Unpaid Principal Balance	7,753	9,602
Related Allowance
Average Recorded Investment	9,438	9,679
Interest Income Recognized	329	287
With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	11,277	17,435
Unpaid Principal Balance	12,932	19,285
Related Allowance	2,692	4,516
Average Recorded Investment	10,581	24,950
Interest Income Recognized	276	468
Residential 1-4 Family [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,001	4,329
Unpaid Principal Balance	1,968	4,590
Related Allowance	316	1,150
Average Recorded Investment	2,222	8,054
Interest Income Recognized	73	203
Residential 1-4 Family [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	864	357
Unpaid Principal Balance	854	404
Related Allowance
Average Recorded Investment	811	2,947
Interest Income Recognized	37	16
Residential 1-4 Family [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	1,137	3,972
Unpaid Principal Balance	1,114	4,186
Related Allowance	316	1,150
Average Recorded Investment	1,411	5,107
Interest Income Recognized	36	187
Multifamily [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Multifamily [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Multifamily [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Construction [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,427	3,806
Unpaid Principal Balance	2,427	3,806
Related Allowance	501	950
Average Recorded Investment	3,316	8,124
Interest Income Recognized		11
Construction [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		1,393
Unpaid Principal Balance		1,393
Related Allowance
Average Recorded Investment	897	2,265
Interest Income Recognized		11
Construction [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,427	2,413
Unpaid Principal Balance	2,427	2,413
Related Allowance	501	950
Average Recorded Investment	2,419	5,859
Interest Income Recognized
Farmland [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	703	131
Unpaid Principal Balance	702	131
Related Allowance	122	57
Average Recorded Investment	788	1,818
Interest Income Recognized	5	8
Farmland [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Farmland [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	703	131
Unpaid Principal Balance	702	131
Related Allowance	122	57
Average Recorded Investment	788	1,818
Interest Income Recognized	5	8
Equity Lines of Credit [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		174
Unpaid Principal Balance		174
Related Allowance		10
Average Recorded Investment		175
Interest Income Recognized		9
Equity Lines of Credit [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Equity Lines of Credit [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		174
Unpaid Principal Balance		174
Related Allowance		10
Average Recorded Investment		175
Interest Income Recognized		9
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment		52
Interest Income Recognized
Commercial [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment		52
Interest Income Recognized
Commercial [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Agricultural [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Agricultural [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment
Unpaid Principal Balance
Related Allowance
Average Recorded Investment
Interest Income Recognized
Commercial Real Estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	13,926	17,823
Unpaid Principal Balance	15,588	19,425
Related Allowance	1,753	2,300
Average Recorded Investment	13,491	15,584
Interest Income Recognized	527	524
Commercial Real Estate [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,916	7,234
Unpaid Principal Balance	6,899	7,199
Related Allowance
Average Recorded Investment	7,528	3,750
Interest Income Recognized	292	260
Commercial Real Estate [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment	7,010	10,589
Unpaid Principal Balance	8,689	12,226
Related Allowance	1,753	2,300
Average Recorded Investment	5,963	11,834
Interest Income Recognized	235	264
Second Mortgages [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		762
Unpaid Principal Balance		761
Related Allowance		49
Average Recorded Investment	202	822
Interest Income Recognized
Second Mortgages [Member] | With No Related Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		606
Unpaid Principal Balance		606
Related Allowance
Average Recorded Investment	202	665
Interest Income Recognized
Second Mortgages [Member] | With Allowance Recorded [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment		156
Unpaid Principal Balance		155
Related Allowance		49
Average Recorded Investment		157
Interest Income Recognized