Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Measurement Input [Extensible List]	us-gaap:MeasurementInputComparabilityAdjustmentMember
Residential Mortgage Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Capitalized servicing rights	$ 231,204	$ 244,411	$ 120,509	$ 114,978
Capitalized servicing rights, valuation allowance	$ (30,000)	(7,000)
Weighted-average prepayment speeds	14.50%
Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rates for fair value estimations	15.00%
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Discount rates for fair value estimations	90.00%
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Change in fair value of nonrecurring fair value measured loans for charge-offs and impairment reserves	$ 222,000	110,000	83,000
Significant Unobservable Inputs (Level 3) [Member] | Residential Mortgage Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Capitalized servicing rights	159,000	188,000
Capitalized servicing rights, valuation allowance	30,000	7,000
Changes in fair value recognized for impairment of capitalized servicing rights	$ 23,000	$ 7,000
Weighted-average prepayment speeds	16.01%	18.50%
Discounted rate represented weighted-average option-adjusted basis spread point percentage	900.00%	900.00%
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	$ 652,000	$ 305,000	268,000
Assets taken in foreclosure of defaulted loans measured at fair value on a nonrecurring basis	22,000	21,000
Fair Value, Measurements, Nonrecurring [Member] | Significant Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	339,000	115,000	120,000
Fair Value, Measurements, Nonrecurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Loans measured at fair value on nonrecurring basis	$ 313,000	$ 190,000	$ 148,000