Fair Value - Fair Value Measurement (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assumed Gain/(Loss) From Loan Sale	$ 2,770
Interest Rate Movement Effect	(3,640)
Servicing Rights Value	11,519
Security Price Change	3,403
Total Fair Value Measurement Gain/(Loss)	14,052	$ 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	961,557
Assumed Gain/(Loss) From Loan Sale	1,912
Interest Rate Movement Effect	(2,466)
Servicing Rights Value	8,516
Total Fair Value Measurement Gain/(Loss)	7,962
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	1,107,575
Security Price Change	3,403
Total Fair Value Measurement Gain/(Loss)	3,403
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	858
Interest Rate Movement Effect	(1,174)
Servicing Rights Value	3,003
Fair value, option, changes in fair value, gain (loss)	2,687	10,042
Fair Value, principal amount, loans held for sale	$ 284,838	$ 439,718