Changes in Fair Value Related to Initial Measurement and Subsequent Changes in Fair Value Included in Earnings for Assets Measured at Fair Value, by Income Statement Line Item (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Changes in fair value included in net income:
Mortgage banking noninterest income (loss)	$ (610)	$ 4,901	$ (2,192)	$ 6,352