Fair Value Measurements and Fair Value of Financial Instruments (Assets Measured at Fair Value on a Non-Recurring Basis) (Detail)	6 Months Ended
	Jun. 30, 2013
Impaired Loans [Member] | Residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Appraisals of collateral value
Impaired Loans [Member] | Residential | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	25.00%
Impaired Loans [Member] | Residential | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	0.00%
Impaired Loans [Member] | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Discounted cash flow model
Impaired Loans [Member] | Commercial | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	6.00%
Impaired Loans [Member] | Commercial | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	0.00%
Impaired Loans [Member] | Commercial Real Estate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Appraisals of collateral value
Impaired Loans [Member] | Commercial Real Estate | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	12.00%
Impaired Loans [Member] | Commercial Real Estate | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	8.00%
Impaired Loans [Member] | Construction
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Appraisals of collateral value
Range of Unobservable Inputs	5.00%
Other Real Estate [Member] | Residential
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Appraisals of collateral value
Other Real Estate [Member] | Residential | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	25.00%
Other Real Estate [Member] | Residential | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Range of Unobservable Inputs	0.00%
Other Real Estate [Member] | Commercial
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Valuation Techniques	Appraisals of collateral value
Range of Unobservable Inputs	15.00%