XML 107 R70.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Fair Value Summary of Quantitative Information about Level 3 Fair Value Measurements (Detail) $ / shares in Units, $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) security $ / shares | Dec. 31, 2016 USD ($) security
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | $ 27,274.7 | $ 23,482.6
Equity securities | Nonredeemable preferred stocks |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 803.8 | 853.5
Fixed maturities |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 20,201.7 | 16,243.8
Fixed maturities | Commercial mortgage-backed securities |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 2,758.6 | 2,253.4
Fair Value, Inputs, Level 3 |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 5.3 | 0.7
Fair Value, Inputs, Level 3 | Third Party Pricing Exemption Securities [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 0.3 | 0.4
Fair Value, Inputs, Level 3 | Total Quantitative Level Three Securities [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | $ 5.0 | $ 0.3
Fair Value, Inputs, Level 3 | Internal Pricing |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Number of securities | security | 1 | 0
Fair Value | $ 5.0 |
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 5.0 | $ 0.0
Fair Value, Inputs, Level 3 | Equity securities | Nonredeemable preferred stocks | Internal Pricing |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | $ 5.0 | 0.0
Valuation Technique | Internal price |
Fair Value Inputs, Original Issue Price | $ / shares | $ 3.9 |
Fair Value, Inputs, Level 3 | Fixed maturities |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | $ 0.0 | 0.3
Fair Value, Inputs, Level 3 | Fixed maturities | External Pricing [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Fair Value | 0.0 | $ 0.3
Fair Value, Inputs, Level 3 | Fixed maturities | Commercial mortgage-backed securities | External Pricing [Member] |  |
Fair Value Inputs, Assets, Quantitative Information [Line Items] |  |
Number of securities | security |  | 1
Fair Value | $ 0.0 | $ 0.3
Fair Value Inputs, Prepayment Rate |  | 0.00%
Valuation Technique |  | External vendor

X
- Definition Original issue price per share used as market price for current quarter acquisition. The inputs used to measure this fair value are initially unobservable. + References No definition available. + Details
Name: | pgr_FairValueInputsOriginalIssuePrice
Namespace Prefix: | pgr_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Securities + References No definition available. + Details
Name: | pgr_NumberOfSecurities
Namespace Prefix: | pgr_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 5 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562 + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- 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_FairValueInputsAssetsQuantitativeInformationLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Rate at which loans or a loan portfolio are expected to prepay principal balances, used as an input to measure fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueInputsPrepaymentRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Description of the inputs and valuation technique(s) used to measure fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (bbb) -URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258 + Details
Name: | us-gaap_FairValueMeasurementsValuationTechniques
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_NonredeemablePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=us-gaap_FixedMaturitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CommercialMortgageBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=pgr_ThirdPartyPricingExemptionSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=pgr_TotalQuantitativeLevelThreeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=pgr_InternalPricingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=pgr_ExternalPricingMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |