Fair Value Measurements - Amount of Net Gains (Losses) from Fair Value Changes (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Net Gains Losses From Change In Fair Value Of Mortgages Loans Held For Sale	$ (331)	$ 32	$ (1,472)	$ 871
Net Gains Losses From Change In Fair Value Of Mortgages Loans Held For Investment	$ (172)	$ 344	$ (921)	$ (65)