Summary of Investments - Fair Value of Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
AVAILABLE-FOR-SALE
Cost or Amortized Cost	$ 1,656,797	$ 1,720,291
Allowance for Credit Losses	0	5
Carrying Value	1,719,790	1,825,438
Fixed Maturities
AVAILABLE-FOR-SALE
Cost or Amortized Cost	1,656,797	1,720,291
Gross Unrealized Appreciation	71,642	107,003
Gross Unrealized Depreciation	8,649	1,851
Fair Value	1,719,790	1,825,443
Allowance for Credit Losses	0	5
Carrying Value	1,719,790	1,825,438
U.S. Treasury
AVAILABLE-FOR-SALE
Cost or Amortized Cost	42,425	149,481
Gross Unrealized Appreciation	216	482
Gross Unrealized Depreciation	718	25
Fair Value	41,923	149,938
Allowance for Credit Losses	0	0
Carrying Value	41,923	149,938
U.S. government agency
AVAILABLE-FOR-SALE
Cost or Amortized Cost	60,074	60,502
Gross Unrealized Appreciation	2,155	4,016
Gross Unrealized Depreciation	562	0
Fair Value	61,667	64,518
Allowance for Credit Losses	0	0
Carrying Value	61,667	64,518
States, municipalities and political subdivisions \| General obligations \| Midwest
AVAILABLE-FOR-SALE
Cost or Amortized Cost	71,863	77,933
Gross Unrealized Appreciation	2,483	4,047
Gross Unrealized Depreciation	0	0
Fair Value	74,346	81,980
Allowance for Credit Losses	0	0
Carrying Value	74,346	81,980
States, municipalities and political subdivisions \| General obligations \| Northeast
AVAILABLE-FOR-SALE
Cost or Amortized Cost	22,061	29,071
Gross Unrealized Appreciation	701	1,379
Gross Unrealized Depreciation	0	0
Fair Value	22,762	30,450
Allowance for Credit Losses	0	0
Carrying Value	22,762	30,450
States, municipalities and political subdivisions \| General obligations \| South
AVAILABLE-FOR-SALE
Cost or Amortized Cost	90,171	104,522
Gross Unrealized Appreciation	3,873	5,448
Gross Unrealized Depreciation	0	0
Fair Value	94,044	109,970
Allowance for Credit Losses	0	0
Carrying Value	94,044	109,970
States, municipalities and political subdivisions \| General obligations \| West
AVAILABLE-FOR-SALE
Cost or Amortized Cost	93,968	102,590
Gross Unrealized Appreciation	5,110	7,431
Gross Unrealized Depreciation	0	0
Fair Value	99,078	110,021
Allowance for Credit Losses	0	0
Carrying Value	99,078	110,021
States, municipalities and political subdivisions \| Special revenue \| Midwest
AVAILABLE-FOR-SALE
Cost or Amortized Cost	114,997	115,956
Gross Unrealized Appreciation	7,292	9,142
Gross Unrealized Depreciation	0	0
Fair Value	122,289	125,098
Allowance for Credit Losses	0	0
Carrying Value	122,289	125,098
States, municipalities and political subdivisions \| Special revenue \| Northeast
AVAILABLE-FOR-SALE
Cost or Amortized Cost	55,811	56,317
Gross Unrealized Appreciation	3,921	4,759
Gross Unrealized Depreciation	0	0
Fair Value	59,732	61,076
Allowance for Credit Losses	0	0
Carrying Value	59,732	61,076
States, municipalities and political subdivisions \| Special revenue \| South
AVAILABLE-FOR-SALE
Cost or Amortized Cost	201,383	208,739
Gross Unrealized Appreciation	14,365	17,967
Gross Unrealized Depreciation	78	0
Fair Value	215,670	226,706
Allowance for Credit Losses	0	0
Carrying Value	215,670	226,706
States, municipalities and political subdivisions \| Special revenue \| West
AVAILABLE-FOR-SALE
Cost or Amortized Cost	126,521	129,417
Gross Unrealized Appreciation	8,128	9,982
Gross Unrealized Depreciation	0	0
Fair Value	134,649	139,399
Allowance for Credit Losses	0	0
Carrying Value	134,649	139,399
Foreign bonds
AVAILABLE-FOR-SALE
Cost or Amortized Cost	30,314	27,799
Gross Unrealized Appreciation	789	1,805
Gross Unrealized Depreciation	197	2
Fair Value	30,906	29,602
Allowance for Credit Losses	0	0
Carrying Value	30,906	29,602
Public utilities
AVAILABLE-FOR-SALE
Cost or Amortized Cost	104,008	76,114
Gross Unrealized Appreciation	3,966	7,388
Gross Unrealized Depreciation	481	0
Fair Value	107,493	83,502
Allowance for Credit Losses	0	0
Carrying Value	107,493	83,502
Corporate bonds \| Energy
AVAILABLE-FOR-SALE
Cost or Amortized Cost	31,011	22,441
Gross Unrealized Appreciation	1,751	2,895
Gross Unrealized Depreciation	81	0
Fair Value	32,681	25,336
Allowance for Credit Losses	0	0
Carrying Value	32,681	25,336
Corporate bonds \| Industrials
AVAILABLE-FOR-SALE
Cost or Amortized Cost	55,014	39,513
Gross Unrealized Appreciation	2,319	3,744
Gross Unrealized Depreciation	162	0
Fair Value	57,171	43,257
Allowance for Credit Losses	0	0
Carrying Value	57,171	43,257
Corporate bonds \| Consumer goods and services
AVAILABLE-FOR-SALE
Cost or Amortized Cost	71,543	46,521
Gross Unrealized Appreciation	1,912	4,046
Gross Unrealized Depreciation	611	0
Fair Value	72,844	50,567
Allowance for Credit Losses	0	0
Carrying Value	72,844	50,567
Corporate bonds \| Health care
AVAILABLE-FOR-SALE
Cost or Amortized Cost	27,351	6,678
Gross Unrealized Appreciation	539	898
Gross Unrealized Depreciation	461	0
Fair Value	27,429	7,576
Allowance for Credit Losses	0	0
Carrying Value	27,429	7,576
Corporate bonds \| Technology, media and telecommunications
AVAILABLE-FOR-SALE
Cost or Amortized Cost	55,405	37,270
Gross Unrealized Appreciation	2,958	4,381
Gross Unrealized Depreciation	866	15
Fair Value	57,497	41,636
Allowance for Credit Losses	0	0
Carrying Value	57,497	41,636
Corporate bonds \| Financial services
AVAILABLE-FOR-SALE
Cost or Amortized Cost	98,352	93,736
Gross Unrealized Appreciation	4,394	7,564
Gross Unrealized Depreciation	131	269
Fair Value	102,615	101,031
Allowance for Credit Losses		5
Carrying Value	102,615	101,026
Mortgage-backed securities
AVAILABLE-FOR-SALE
Cost or Amortized Cost	25,075	20,305
Gross Unrealized Appreciation	167	326
Gross Unrealized Depreciation	229	54
Fair Value	25,013	20,577
Allowance for Credit Losses	0	0
Carrying Value	25,013	20,577
Collateralized mortgage obligations \| Government national mortgage association
AVAILABLE-FOR-SALE
Cost or Amortized Cost	109,968	81,758
Gross Unrealized Appreciation	2,322	4,439
Gross Unrealized Depreciation	1,772	45
Fair Value	110,518	86,152
Allowance for Credit Losses	0	0
Carrying Value	110,518	86,152
Collateralized mortgage obligations \| Federal home loan mortgage corporation
AVAILABLE-FOR-SALE
Cost or Amortized Cost	120,911	151,362
Gross Unrealized Appreciation	736	2,239
Gross Unrealized Depreciation	1,658	758
Fair Value	119,989	152,843
Allowance for Credit Losses	0	0
Carrying Value	119,989	152,843
Collateralized mortgage obligations \| Federal national mortgage association
AVAILABLE-FOR-SALE
Cost or Amortized Cost	48,246	81,952
Gross Unrealized Appreciation	945	2,013
Gross Unrealized Depreciation	642	683
Fair Value	48,549	83,282
Allowance for Credit Losses	0	0
Carrying Value	48,549	83,282
Asset-backed securities
AVAILABLE-FOR-SALE
Cost or Amortized Cost	325	314
Gross Unrealized Appreciation	600	612
Gross Unrealized Depreciation	0	0
Fair Value	925	926
Allowance for Credit Losses	0	0
Carrying Value	$ 925	$ 926

Debt Securities, Available-for-Sale, Excluding Accrued Interest, Before Allowance For Credit Loss

No definition available.

Name:	ufcs_DebtSecuritiesAvailableForSaleExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix:	ufcs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on 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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123581744&loc=d3e27161-111563

+ Details

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

- References

No definition available.

+ Details

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

- Definition

Amount excluding accrued interest, of allowance for credit loss on 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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

+ Details

Name:	us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostAllowanceForCreditLossExcludingAccruedInterest
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amortized cost excluding accrued interest, before allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

+ Details

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

- Definition

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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

+ Details

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