Loans Receivable - Performing and Nonperforming Single Family Residential and Consumer Loans Based on Payment Activity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 726,571	$ 716,239
Residential Real Estate, Single Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	347,223	341,775
Consumer Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	84,504	82,987
Consumer Dealer Auto and RV Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	49,437	46,502
Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,047	6,653
Single Family Residential and Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	487,211	477,917
Single Family Residential and Consumer Loans [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	483,408	474,014
Single Family Residential and Consumer Loans [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,803	3,903
Single Family Residential and Consumer Loans [Member] | Residential Real Estate, Single Family [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	347,223	341,775
Single Family Residential and Consumer Loans [Member] | Residential Real Estate, Single Family [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	343,873	338,370
Single Family Residential and Consumer Loans [Member] | Residential Real Estate, Single Family [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	3,350	3,405
Single Family Residential and Consumer Loans [Member] | Consumer Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	84,504	82,987
Single Family Residential and Consumer Loans [Member] | Consumer Home Equity [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	84,272	82,692
Single Family Residential and Consumer Loans [Member] | Consumer Home Equity [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	232	295
Single Family Residential and Consumer Loans [Member] | Consumer Dealer Auto and RV Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	49,437	46,502
Single Family Residential and Consumer Loans [Member] | Consumer Dealer Auto and RV Loans [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	49,291	46,364
Single Family Residential and Consumer Loans [Member] | Consumer Dealer Auto and RV Loans [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	146	138
Single Family Residential and Consumer Loans [Member] | Consumer Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	6,047	6,653
Single Family Residential and Consumer Loans [Member] | Consumer Other [Member] | Performing [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	5,972	6,588
Single Family Residential and Consumer Loans [Member] | Consumer Other [Member] | Nonperforming [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable	$ 75	$ 65