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, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Aggregate fair value	$ 210,866		$ 210,866		$ 166,247
Aggregate unpaid principal	203,293		203,293		161,083
Aggregate fair value less unpaid principal	7,573		7,573		$ 5,164
Net gain (loss) on change in Fair Value	$ (1,500)	$ 7	$ 2,400	$ 3,700