Fair Value of Financial Instruments - Quantitative Information About Level 3 Fair Value Measurements (Details) $ in Thousands	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 1,638,512	$ 1,551,336
Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	3,894	4,253
Recurring
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	1,638,638	1,551,339
Recurring \| Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	3,894	4,253
Recurring \| Level 3
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	5,499	6,476
Recurring \| Level 3 \| Corporate bonds
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 4,700
Recurring \| Level 3 \| Corporate bonds \| Third-party Valuation \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, range of weighted average significant unobservable inputs	0.900
Recurring \| Level 3 \| Corporate bonds \| Third-party Valuation \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, range of weighted average significant unobservable inputs	1.000
Recurring \| Level 3 \| Asset-backed securities
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities	$ 799	$ 801
Recurring \| Level 3 \| Asset-backed securities \| Discounted cash flow \| Minimum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, range of weighted average significant unobservable inputs	0.04
Recurring \| Level 3 \| Asset-backed securities \| Discounted cash flow \| Maximum
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Available-for-sale securities, range of weighted average significant unobservable inputs	0.06

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Value of input used to measure investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleMeasurementInput
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=ufcs_ThirdPartyValuationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_ValuationTechniqueDiscountedCashFlowMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: