Income Taxes - Summary of Differences in Taxes from Continuing Operations Computed at Statutory Rate (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Income Tax Disclosure [Abstract]
Statutory rate	21.00%
Provision at statutory rate	$ 5,372	$ 14,570
Tax-exempt interest	(2,632)	(2,531)
Section 291/265 interest disallowance	73	111
Company-owned life insurance income	(647)	(669)
Tax-exempt income	(3,206)	(3,089)
State income taxes	(8)	1,999
Interim period effective rate adjustment	3,267	688
Tax credit investments - federal	(1,902)	(420)
Other, net	(584)	(644)
Income tax expense	$ 2,939	$ 13,104
Effective tax rate	11.50%	18.90%

Income tax reconciliation, non-deductible expense, interest disallowance.

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Income tax reconciliation tax exempt interest.

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Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to income (loss) exempt from income taxes.

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