Fair Value Measurements (Details) - USD ($) | Mar. 31, 2017 | Dec. 31, 2016 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | $ 2,279,000,000 | $ 2,432,000,000 |
Total assets | 3,026,000,000 | 3,185,000,000 |
U.S. government and agencies | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 104,000,000 | 117,000,000 |
State and political subdivisions | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 590,000,000 | 615,000,000 |
Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 1,420,000,000 | 1,533,000,000 |
Mortgage-backed/asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 55,000,000 | 58,000,000 |
Foreign government bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 110,000,000 | 109,000,000 |
Preferred stock available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 322,000,000 | 315,000,000 |
Equity securities available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 425,000,000 | 438,000,000 |
Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Assets held at fair value | 0 | 0 |
Liabilities held at fair value | 0 | 0 |
Fair value, measurements, recurring | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 3,026,000,000 | 3,185,000,000 |
Fair value, measurements, recurring | U.S. government and agencies | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 104,000,000 | 117,000,000 |
Fair value, measurements, recurring | State and political subdivisions | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 590,000,000 | 615,000,000 |
Fair value, measurements, recurring | Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 1,420,000,000 | 1,533,000,000 |
Fair value, measurements, recurring | Mortgage-backed/asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 55,000,000 | 58,000,000 |
Fair value, measurements, recurring | Foreign government bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 110,000,000 | 109,000,000 |
Fair value, measurements, recurring | Preferred stock available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 322,000,000 | 315,000,000 |
Fair value, measurements, recurring | Equity securities available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 425,000,000 | 438,000,000 |
Fair value, measurements, recurring | Level 1 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 458,000,000 | 470,000,000 |
Fair value, measurements, recurring | Level 1 | U.S. government and agencies | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 1 | State and political subdivisions | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Mortgage-backed/asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Foreign government bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 1 | Preferred stock available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 33,000,000 | 32,000,000 |
Fair value, measurements, recurring | Level 1 | Equity securities available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 425,000,000 | 438,000,000 |
Fair value, measurements, recurring | Level 2 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 2,568,000,000 | 2,715,000,000 |
Fair value, measurements, recurring | Level 2 | U.S. government and agencies | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 104,000,000 | 117,000,000 |
Fair value, measurements, recurring | Level 2 | State and political subdivisions | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 590,000,000 | 615,000,000 |
Fair value, measurements, recurring | Level 2 | Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 1,420,000,000 | 1,533,000,000 |
Fair value, measurements, recurring | Level 2 | Mortgage-backed/asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 55,000,000 | 58,000,000 |
Fair value, measurements, recurring | Level 2 | Foreign government bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 110,000,000 | 109,000,000 |
Fair value, measurements, recurring | Level 2 | Preferred stock available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 289,000,000 | 283,000,000 |
Fair value, measurements, recurring | Level 2 | Equity securities available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 0 | 0 |
Fair value, measurements, recurring | Level 3 | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Total assets | 0 | 0 |
Fair value, measurements, recurring | Level 3 | U.S. government and agencies | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 3 | State and political subdivisions | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Corporate debt securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Mortgage-backed/asset-backed securities | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Foreign government bonds | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Fixed maturity securities available for sale | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Preferred stock available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | 0 | 0 |
Fair value, measurements, recurring | Level 3 | Equity securities available for sale | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | |
Equity securities available for sale, at fair value | $ 0 | $ 0 |