Loans - Risk Category of Loans by Class of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	$ 1,184,820	$ 1,164,883
Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,133,025	1,109,057
Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	14,097	18,273
Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	37,698	37,553
Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	37,698	37,553
Commercial Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	270,405	252,911
Commercial Loans [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	229,650	209,026
Commercial Loans [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	13,939	17,324
Commercial Loans [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	26,816	26,561
Commercial Loans [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	26,816	26,561
Commercial Loans [Member] | Multifamily [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	63,597	60,546
Commercial Loans [Member] | Multifamily [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	58,884	53,485
Commercial Loans [Member] | Multifamily [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,852	4,134
Commercial Loans [Member] | Multifamily [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	2,861	2,927
Commercial Loans [Member] | Multifamily [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	2,861	2,927
Commercial Loans [Member] | Nonresidential [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	132,305	121,595
Commercial Loans [Member] | Nonresidential [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	103,515	92,074
Commercial Loans [Member] | Nonresidential [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	12,087	12,290
Commercial Loans [Member] | Nonresidential [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	16,703	17,231
Commercial Loans [Member] | Nonresidential [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	16,703	17,231
Commercial Loans [Member] | Land [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	9,437	9,484
Commercial Loans [Member] | Land [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8,905	8,952
Commercial Loans [Member] | Land [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	532	532
Commercial Loans [Member] | Land [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	532	532
Commercial Loans [Member] | Construction [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	11,030	16,064
Commercial Loans [Member] | Construction [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	9,980	15,013
Commercial Loans [Member] | Construction [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,050	1,051
Commercial Loans [Member] | Construction [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,050	1,051
Commercial Loans [Member] | Secured [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	53,598	45,088
Commercial Loans [Member] | Secured [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	48,037	39,480
Commercial Loans [Member] | Secured [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans		900
Commercial Loans [Member] | Secured [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	5,561	4,708
Commercial Loans [Member] | Secured [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	5,561	4,708
Commercial Loans [Member] | Unsecured [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	438	134
Commercial Loans [Member] | Unsecured [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	329	22
Commercial Loans [Member] | Unsecured [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	109	112
Commercial Loans [Member] | Unsecured [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	109	112
Residential Mortgage Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	733,680	731,218
Residential Mortgage Loans [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	725,076	721,892
Residential Mortgage Loans [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	150	939
Residential Mortgage Loans [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8,454	8,387
Residential Mortgage Loans [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8,454	8,387
Residential Mortgage Loans [Member] | Construction [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	37,293	37,113
Residential Mortgage Loans [Member] | Construction [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	37,293	37,113
Residential Mortgage Loans [Member] | One-to Four-Family [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	696,387	694,105
Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	687,783	684,779
Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	150	939
Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8,454	8,387
Residential Mortgage Loans [Member] | One-to Four-Family [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8,454	8,387
Consumer Loans [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	180,735	180,754
Consumer Loans [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	178,299	178,139
Consumer Loans [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8	10
Consumer Loans [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	2,428	2,605
Consumer Loans [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	2,428	2,605
Consumer Loans [Member] | Home Equity [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	155,002	154,776
Consumer Loans [Member] | Home Equity [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	153,047	152,599
Consumer Loans [Member] | Home Equity [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,955	2,177
Consumer Loans [Member] | Home Equity [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,955	2,177
Consumer Loans [Member] | Auto [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	7,154	5,902
Consumer Loans [Member] | Auto [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	7,105	5,829
Consumer Loans [Member] | Auto [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans		10
Consumer Loans [Member] | Auto [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	49	63
Consumer Loans [Member] | Auto [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	49	63
Consumer Loans [Member] | Marine [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	3,301	3,917
Consumer Loans [Member] | Marine [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	3,000	3,766
Consumer Loans [Member] | Marine [Member] | Special Mention [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	8
Consumer Loans [Member] | Marine [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	293	151
Consumer Loans [Member] | Marine [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	293	151
Consumer Loans [Member] | Recreational Vehicle [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	13,447	14,054
Consumer Loans [Member] | Recreational Vehicle [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	13,321	13,846
Consumer Loans [Member] | Recreational Vehicle [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	126	208
Consumer Loans [Member] | Recreational Vehicle [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	126	208
Consumer Loans [Member] | Other [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,831	2,105
Consumer Loans [Member] | Other [Member] | Unclassified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	1,826	2,099
Consumer Loans [Member] | Other [Member] | Substandard [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	5	6
Consumer Loans [Member] | Other [Member] | Classified [Member]
Financing Receivable Modifications Number Of Contracts [Line Items]
Total loans	$ 5	$ 6