Fair Value Disclosures - Assets Measured at Fair Value on Non-recurring Basis (Detail) (Fair Value, Measurements, Nonrecurring [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans held for investment	$ 63,708	$ 44,976
Mortgage servicing rights		4,152
Other real estate owned		1,607
Total assets	63,708	50,735
Level 1 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans held for investment
Mortgage servicing rights
Other real estate owned
Total assets
Level 2 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans held for investment
Mortgage servicing rights		4,152
Other real estate owned		1,607
Total assets		5,759
Level 3 [Member]
Fair Value Of Assets And Liabilities Measured On Non Recurring Basis [Line Items]
Impaired loans held for investment	63,708	44,976
Mortgage servicing rights
Other real estate owned
Total assets	$ 63,708	$ 44,976