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
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Loans held fro investment at fair value	$ 14,000		$ 12,700
Mortgages Held For Sale at Fair Value
Aggregate fair value	122,333		157,041
Aggregate unpaid principal	118,875		153,801
Aggregate fair value less unpaid principal	3,458		$ 3,240
Total mortgage income (loss) in the Consolidated Statement of Comprehensive Income	$ 400	$ 1,900