Fair Value Measurements - Amount of Net Gains (Losses) from Fair Value Changes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Mortgage loans held for sale, at fair value	$ 2,879	$ (331)	$ 3,531	$ (1,472)
Mortgage loans held for investment, at fair value	$ (104)	$ (172)	$ 87	$ (921)