Fair Value Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2013
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Percentage of cost to sale of non-covered impaired loans and non-covered other real estate owned	8.00%
Minimum [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Term of interest rate swap contracts by the counterparty, years	3 years
Maximum [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Term of interest rate swap contracts by the counterparty, years	30 years