Derivatives - Gains and Losses on Derivative Contracts Included on Condensed Consolidated Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Rate Lock Commitments [Member] | Compensation and Employee Benefits [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	$ (200)	$ (1,300)	$ 1,600	$ 2,000
Not Designated as Hedging Instrument [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	(2,232)	7,439	(36,092)	20,935
Not Designated as Hedging Instrument [Member] | Rate Lock Commitments [Member] | Gains From Mortgage Banking Activities/Originations, Net [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	5,734	(7,656)	27,113	(3,872)
Not Designated as Hedging Instrument [Member] | Rate Lock Commitments [Member] | Compensation and Employee Benefits [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	236	1,284	(1,620)	(1,998)
Not Designated as Hedging Instrument [Member] | Nasdaq Forward [Member] | Other Income, Net [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	(8,214)	9,135	(37,181)	6,327
Not Designated as Hedging Instrument [Member] | Forward Sale Contracts [Member] | Deliver Loans to Third-party Investors [Member] | Gains From Mortgage Banking Activities/Originations, Net [Member]
Derivative Instruments Gain Loss [Line Items]
Gain (loss) recognized in income for derivatives	$ 12	$ 4,676	$ (24,404)	$ 20,478