Loans - Loans by Class Modified as Troubled Debt Restructurings with Payment Default (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2013 SecurityLoan	Dec. 31, 2012 SecurityLoan
Financing Receivable, Recorded Investment [Line Items]
Number of loans	18	11
Recorded Investment	$ 2,608	$ 928
Permanent Real Estate Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	9	9
Recorded Investment	1,338	851
Permanent Real Estate Loans [Member] | One-to Four-Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	7	9
Recorded Investment	851	851
Permanent Real Estate Loans [Member] | Multi-Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Permanent Real Estate Loans [Member] | Nonresidential [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Permanent Real Estate Loans [Member] | Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	2
Recorded Investment	487
Construction Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	1
Recorded Investment	823
Construction Loans [Member] | One-to Four-Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	1
Recorded Investment	823
Construction Loans [Member] | Multi-Family and Nonresidential [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Consumer Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	8	2
Recorded Investment	447	77
Consumer Loans [Member] | Home Equity [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	7	2
Recorded Investment	354	77
Consumer Loans [Member] | Auto [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Consumer Loans [Member] | Marine [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Consumer Loans [Member] | Recreational Vehicles [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans	1
Recorded Investment	93
Consumer Loans [Member] | Others [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Commercial Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Commercial Loans [Member] | Secured [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment
Commercial Loans [Member] | Unsecured [Member]
Financing Receivable, Recorded Investment [Line Items]
Number of loans
Recorded Investment