Fair Value - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Provision for credit losses	$ 16,950	$ 1,043
Net carrying amount other real estate owned and other repossessed property	200		$ 43
Other real estate owned property write-downs	11
Valuation allowance for loan servicing rights with impairments	1,443	17	31	$ 15
Impairments of loan servicing rights	$ 1,412	2
Past due period of mortgage loans held for sale, days	90 days
Interest income for residential loans held for sale	$ 400	200
States and political subdivisions
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Transfers out of Level 3		4,033
Impaired Commercial and Commercial Real Estate Loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Principal amount of impaired commercial and commercial real estate loans	49,500		30,900
Valuation allowance	10,600		$ 8,900
Provision for credit losses	$ 6,800	$ 1,200