Fair Value - Fair Value Measurement (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	$ 8,712
Interest Rate Movement Effect	(14,907)
Servicing Rights Value	11,863
Security Price Change	10,463
Total Fair Value Measurement Gain/(Loss)	16,131	$ 15,583
Mortgage Banking | Level 2 | Fair Value, Recurring | Rate Lock Commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	1,239,365
Assumed Gain/(Loss) From Loan Sale	6,787
Interest Rate Movement Effect	(7,645)
Servicing Rights Value	8,752
Total Fair Value Measurement Gain/(Loss)	7,894
Mortgage Banking | Level 2 | Fair Value, Recurring | Forward Sales Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value disclosure, off-balance sheet risks, face amount, liability	1,392,437
Security Price Change	10,463
Total Fair Value Measurement Gain/(Loss)	10,463
Mortgage Banking | Level 2 | Fair Value, Recurring | Mortgages Held for Sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	1,925
Interest Rate Movement Effect	(7,262)
Servicing Rights Value	3,111
Fair value, option, changes in fair value, gain (loss)	(2,226)	10,042
Fair Value, principal amount, loans held for sale	$ 337,008	$ 439,718