Allowance for Loan Losses - Performing and Non Performing Loans (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014		Dec. 31, 2013
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	$ 153,256		$ 144,489
Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	121,641	[1]	114,458	[2]
Residential Revolving and Junior Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	25,816	[3]	24,045	[4]
Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	5,799	[5]	5,986	[6]
Substandard | Residential First Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	2,300		2,600
Substandard | Residential Revolving and Junior Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	155		216
Substandard | Consumer Loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Risk rating grade totaled	$ 7		$ 9

[1] Residential First Mortgages which have been assigned a risk rating grade of Substandard totaled $2.3 million as of June 30, 2014.

[2] Residential First Mortgages which have been assigned a risk rating grade of Substandard totaled $2.6 million as of December 31, 2013.

[3] Residential Revolving and Junior Mortgages which have been assigned a risk rating grade of Substandard totaled $155 thousand as of June 30, 2014.

[4] Residential Revolving and Junior Mortgages which have been assigned a risk rating grade of Substandard totaled $216 thousand as of December 31, 2013.

[5] Consumer Loans which have been assigned a risk rating grade of Substandard totaled $7 thousand as of June 30, 2014.

[6] Consumer Loans which have been assigned a risk rating grade of Substandard totaled $9 thousand as of December 31, 2013.