Fair Value Summary of Changes in Fair Value Associated With Level 3 Assets (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2022	Dec. 31, 2021
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	$ 127.7	$ 54.8
Calls/ Maturities/ Paydowns	2.4	13.8
Purchases	2.5	67.2
Sales	(15.0)	(11.0)
Net Realized (Gain)/Loss on Sales	(17.2)	(13.2)
Change in Valuation	3.2	66.1
Net Transfers In (Out)	18.3	(50.0)
Ending Fair value	$ 121.9	127.7
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on security sales
Equity securities \| Nonredeemable preferred stocks \| Financials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	$ 76.4	10.0
Calls/ Maturities/ Paydowns	0.0	0.0
Purchases	2.5	60.2
Sales	(15.0)	0.0
Net Realized (Gain)/Loss on Sales	(17.2)	0.0
Change in Valuation	20.7	6.2
Net Transfers In (Out)	0.0	0.0
Ending Fair value	67.4	76.4
Equity securities \| Nonredeemable preferred stocks \| Industrials
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	34.4	16.7
Calls/ Maturities/ Paydowns	(0.5)	0.0
Purchases	0.0	5.0
Sales	0.0	(5.0)
Net Realized (Gain)/Loss on Sales	0.0	(4.5)
Change in Valuation	(17.5)	22.2
Net Transfers In (Out)	0.0	0.0
Ending Fair value	16.4	34.4
Equity securities \| Common equities \| Common Stocks, by Industry
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	0.0	25.0
Calls/ Maturities/ Paydowns	0.0	0.0
Purchases	0.0	2.0
Sales	0.0	(6.0)
Net Realized (Gain)/Loss on Sales	0.0	(8.7)
Change in Valuation	0.0	37.7
Net Transfers In (Out)	18.3	(50.0)
Ending Fair value	18.3	0.0
Equity securities \| Common equities \| Other risk investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Fair Value	16.9	3.1
Calls/ Maturities/ Paydowns	2.9	13.8
Purchases	0.0	0.0
Sales	0.0	0.0
Net Realized (Gain)/Loss on Sales	0.0	0.0
Change in Valuation	0.0	0.0
Net Transfers In (Out)	0.0	0.0
Ending Fair value	$ 19.8	$ 16.9

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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

- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of increase (decrease) of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)
-URI https://asc.fasb.org/extlink&oid=126976982&loc=d3e19207-110258

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of transfer of financial instrument classified as an asset into (out of) level 3 of the fair value hierarchy.

+ References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

+ References

+ Details

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

- Definition

Indicates line item in statement in which net income is reported that includes gain (loss) from asset measured at fair value using unobservable input (level 3).

+ References

+ Details

Name:	us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList
Namespace Prefix:	us-gaap_
Data Type:	enum2:enumerationSetItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_InvestmentTypeAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	pgr_InvestmentCategoryAxis=us-gaap_BanksTrustAndInsuranceEquitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	pgr_InvestmentCategoryAxis=us-gaap_IndustrialMiscellaneousAndAllOthersMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	pgr_InvestmentCategoryAxis=us-gaap_CommonStocksByIndustryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	pgr_InvestmentCategoryAxis=pgr_OtherRiskInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: