Effect of Derivative Instruments on Consolidated Statements of Income and Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Included in Mortgage Banking Income	$ 3,913	$ (971)	$ 2,990	$ 6,723
Treasury Options
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Included in Mortgage Banking Income	2,485	(2,580)	(2,589)	(1,525)
Eurodollar Futures
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Included in Mortgage Banking Income	1,134	(6)	1,495	100
Forward commitments to buy/sell loans/mortgage-backed securities
Derivative Instruments, Gain (Loss) [Line Items]
Gain (Loss) Included in Mortgage Banking Income	$ 294	$ 1,615	$ 4,084	$ 8,148