Income Taxes - Percentage of Pretax Earnings, Differs from Statutory Federal Income Tax Rate (Detail)	12 Months Ended
Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	21.00%	21.00%	21.00%
Reductions in tax rate resulting from interest income exempt from federal income tax	(3.80%)	(4.40%)	(4.70%)
Other	1.00%	(0.10%)	0.00%
Effective income tax rate	18.20%	16.50%	16.30%

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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
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-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Percentage 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 other adjustments.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479360/740-10-S99-1

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