Fair Value Measurement - Reconciliation of Assets and Liabilities Measured at Fair Value Using Significant Unobservable Inputs on Recurring Basis (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 6,200
Ending Balance		$ 6,200
Mortgage servicing rights
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning Balance	6,200	7,098	$ 6,687
Transfers into (out of) Level 3	0	0	0
Change Included in Earnings	(2,634)	(1,811)	(146)
Issuances	1,526	913	557
Ending Balance	$ 5,092	$ 6,200	$ 7,098