Fair Value Measurements - Summary of Difference Between the Aggregate Fair Value and the Aggregate Unpaid Principal Balance for Mortgage Loans Held for Sale (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Aggregate fair value	$ 202,168		$ 202,168		$ 139,950
Aggregate unpaid principal	194,376		194,376		134,639
Aggregate fair value less unpaid principal	7,792		7,792		$ 5,311
Net gain (loss) on change in Fair Value	$ 600	$ 1,600	$ 2,400	$ 4,000