Differences Between Fair Value Carrying Amount of Loans Held for Sale Measured at Fair Value and Aggregate Unpaid Principal Amount Entitled to Receive at Maturity (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value Disclosures [Abstract]
Fair Value Carrying Amount, Total loans	$ 10,672	$ 55,809
Aggregate Unpaid Principal, Total loans	10,595
Fair Value Carrying Amount Less Aggregate Unpaid Principal, Total loans	$ 77