Derivatives - Summary of Gain (Loss) on Change in Fair Value of Derivatives Included in Condensed Consolidated Statements of Operations (Detail) - Derivatives Not Designed as Hedging Instruments [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	$ 7,035	$ 2,642
Interest Rate Contract [Member] | Rate Lock Commitments [Member] | Gains from Mortgage Banking Activities/Orginations, Net [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	2,269	132
Interest Rate Contract [Member] | Rate Lock Commitments [Member] | Compensation and Employee Benefits [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	(2,500)	(807)
Forward Sale Contracts [Member] | Deliver Loans to Third-party Investors [Member] | Gains from Mortgage Banking Activities/Orginations, Net [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	$ 7,266	$ 3,317