XML 67 R56.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Fair Value Measurements - Fair Value Inputs (Details) - USD ($) $ in Millions | Sep. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value Option Investments, Fair Value Disclosure | $ 0.0 | $ 77.5
Trading Securities, Fair Value Disclosure | 0.0 | 6.7
Fair Value, Inputs, Level 3 [Member] | Partnership Interest [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share, Unfunded Commitments | 149.3 |
Fair Value, Measurements, Recurring [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Trading Securities, Fair Value Disclosure |  | 6.7
Cash Flow Hedge Derivative Instrument Assets at Fair Value |  | (0.8)
Investments, Fair Value Disclosure | 6,924.4 | 5,992.1
Fair Value, Measurements, Recurring [Member] | Investments in Fixed Maturities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 6,108.6 | 5,382.7
Fair Value, Measurements, Recurring [Member] | U.S. Government and Government Agencies and Authorities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 858.9 | 556.1
Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 1,533.5 | 1,701.8
Fair Value, Measurements, Recurring [Member] | Foreign Governments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 5.7 | 3.2
Fair Value, Measurements, Recurring [Member] | Corporate Bonds and Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 3,222.5 | 2,980.6
Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stocks |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 0.1
Fair Value, Measurements, Recurring [Member] | Collateralized Loan Obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 472.1 | 139.8
Fair Value, Measurements, Recurring [Member] | Other Mortgage- and Asset-backed |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 15.9 | 1.1
Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 815.8 | 526.0
Fair Value, Measurements, Recurring [Member] | Exchange Traded Funds [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 549.1 | 219.5
Fair Value, Measurements, Recurring [Member] | Partnership Interest [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 202.2 | 202.9
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Trading Securities, Fair Value Disclosure |  | 6.7
Cash Flow Hedge Derivative Instrument Assets at Fair Value |  | 0.0
Investments, Fair Value Disclosure | 724.8 | 349.7
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Investments in Fixed Maturities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 163.6 | 115.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | U.S. Government and Government Agencies and Authorities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 163.6 | 115.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Foreign Governments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Corporate Bonds and Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Redeemable Preferred Stocks |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Collateralized Loan Obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Mortgage- and Asset-backed |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 561.2 | 227.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Exchange Traded Funds [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 549.1 | 219.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Partnership Interest [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Trading Securities, Fair Value Disclosure |  | 0.0
Cash Flow Hedge Derivative Instrument Assets at Fair Value |  | (0.8)
Investments, Fair Value Disclosure | 5,137.4 | 4,839.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Investments in Fixed Maturities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 5,085.0 | 4,772.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | U.S. Government and Government Agencies and Authorities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 695.3 | 440.3
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 1,531.7 | 1,701.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Foreign Governments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 5.7 | 3.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Bonds and Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 2,841.2 | 2,579.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Redeemable Preferred Stocks |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Collateralized Loan Obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 5.4 | 46.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Mortgage- and Asset-backed |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 5.7 | 1.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 52.4 | 68.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Exchange Traded Funds [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Partnership Interest [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Trading Securities, Fair Value Disclosure |  | 0.0
Cash Flow Hedge Derivative Instrument Assets at Fair Value |  | 0.0
Investments, Fair Value Disclosure | 860.0 | 556.6
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Investments in Fixed Maturities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 860.0 | 494.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | U.S. Government and Government Agencies and Authorities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 1.8 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Foreign Governments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Corporate Bonds and Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 381.3 | 401.5
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Redeemable Preferred Stocks |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 0.1
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Collateralized Loan Obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 466.7 | 93.2
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Mortgage- and Asset-backed |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 10.2 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 61.8
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Exchange Traded Funds [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Partnership Interest [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 34.4
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 39.8 | 55.7
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 11.7 | 7.1
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 11.7 | 7.0
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 39.8 | 55.7
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.1
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 11.9 | 23.1
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 1.1 | 17.7
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.4 | 0.7
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 11.9 | 12.3
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.7 | 0.4
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 10.8
All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 16.6
Limited Liability Companies and Limited Partnership Hedge Funds [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value Option Investments, Fair Value Disclosure |  | 77.5
Limited Liability Companies and Limited Partnership Hedge Funds [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value Option Investments, Fair Value Disclosure |  | 0.0
Limited Liability Companies and Limited Partnership Hedge Funds [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value Option Investments, Fair Value Disclosure |  | 0.0
Limited Liability Companies and Limited Partnership Hedge Funds [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value Option Investments, Fair Value Disclosure |  | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Trading Securities, Fair Value Disclosure |  | 0.0
Cash Flow Hedge Derivative Instrument Assets at Fair Value |  | 0.0
Investments, Fair Value Disclosure | 202.2 | 246.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Investments in Fixed Maturities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | U.S. Government and Government Agencies and Authorities |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | States and Political Subdivisions [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Foreign Governments |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Corporate Bonds and Notes [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Redeemable Preferred Stocks |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure |  | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Collateralized Loan Obligations |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Other Mortgage- and Asset-backed |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Equity Securities [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 202.2 | 168.5
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Exchange Traded Funds [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Fair Value, Measurements, Recurring [Member] | Partnership Interest [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 202.2 | 168.5
Fair Value, Inputs, Net Asset Value [Member] | Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Preferred Stock [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | All Industries Other than Finance, Insurance and Real Estate [Member] | Fair Value, Measurements, Recurring [Member] | Common Stocks [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Available-for-sale Securities, Fair Value Disclosure | $ 0.0 | 0.0
Fair Value, Inputs, Net Asset Value [Member] | Limited Liability Companies and Limited Partnership Hedge Funds [Member] | Fair Value, Measurements, Recurring [Member] |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |
Fair Value Option Investments, Fair Value Disclosure |  | $ 77.5

X
- Definition Amount of investments reported under the Fair Value Option method of accounting. + References No definition available. + Details
Name: | kmpr_FairValueOptionInvestments
Namespace Prefix: | kmpr_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. + References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value of all asset derivatives designated as cash flow hedging instruments. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 10 -Section 50 -Paragraph 4B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=109980867&loc=SL5624163-113959 + Details
Name: | us-gaap_CashFlowHedgeDerivativeInstrumentAssetsAtFairValue
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_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of unfunded commitments for which the entity is obligated, to those certain investments for which net asset value per share is calculated (including by unit, membership interest, or other equity (ownership interest) unit measure) (alternative investments). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 6A -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=99377789&loc=SL6742756-110258 + Details
Name: | us-gaap_FairValueInvestmentsEntitiesThatCalculateNetAssetValuePerShareUnfundedCommittments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + 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 (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
Name: | us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.4) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_TradingSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=srt_PartnershipInterestMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USStatesAndPoliticalSubdivisionsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MandatorilyRedeemablePreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_CollateralizedLoanObligationsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=kmpr_OtherMortgageandAssetbackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_ExchangeTradedFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EquitySecuritiesByIndustryAxis=kmpr_FinanceInsuranceandRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_PreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_EquitySecuritiesByIndustryAxis=kmpr_AllIndustriesOtherthanFinanceInsuranceandRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_ValuationTechniqueAxis=kmpr_FairValueInputsNetAssetValueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |