0001001 - Document - Cover Page link:presentationLink link:calculationLink link:definitionLink 1001002 - Statement - STATEMENTS OF OPERATIONS (UNAUDITED) link:presentationLink link:calculationLink link:definitionLink 1002003 - Statement - STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) link:presentationLink link:calculationLink link:definitionLink 1003004 - Statement - STATEMENTS OF FINANCIAL POSITION link:presentationLink link:calculationLink link:definitionLink 1004005 - Statement - STATEMENTS OF FINANCIAL POSITION (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 1005006 - Statement - STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) link:presentationLink link:calculationLink link:definitionLink 1006007 - Statement - STATEMENTS OF SHAREHOLDERS' EQUITY (UNAUDITED) (Parenthetical) link:presentationLink link:calculationLink link:definitionLink 1007008 - Statement - STATEMENTS OF CASH FLOWS (UNAUDITED) link:presentationLink link:calculationLink link:definitionLink 2101101 - Disclosure - Nature of Operations link:presentationLink link:calculationLink link:definitionLink 2402401 - Disclosure - Nature of Operations (Details) link:presentationLink link:calculationLink link:definitionLink 2103102 - Disclosure - Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 2204201 - Disclosure - Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 2105103 - Disclosure - Revenue link:presentationLink link:calculationLink link:definitionLink 2306301 - Disclosure - Revenue (Tables) link:presentationLink link:calculationLink link:definitionLink 2407402 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 2407402 - Disclosure - Revenue - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 2408403 - Disclosure - Revenue - Disaggregation of Revenues By Performance Obligations (Details) link:presentationLink link:calculationLink link:definitionLink 2109104 - Disclosure - Earnings Per Share link:presentationLink link:calculationLink link:definitionLink 2310302 - Disclosure - Earnings Per Share (Tables) link:presentationLink link:calculationLink link:definitionLink 2411404 - Disclosure - Earnings Per Share - Narrative (Details) link:presentationLink link:calculationLink link:definitionLink 2412405 - Disclosure - Earnings Per Share (Details) link:presentationLink link:calculationLink link:definitionLink 2113105 - Disclosure - Fair Value link:presentationLink link:calculationLink link:definitionLink 2314303 - Disclosure - Fair Value (Tables) link:presentationLink link:calculationLink link:definitionLink 2415406 - Disclosure - Fair Value - Fair Value Measurements on a Recurring Basis by Asset Class and Level of Input (Details) link:presentationLink link:calculationLink link:definitionLink 2416407 - Disclosure - Fair Value - Level 3 Assets (Details) link:presentationLink link:calculationLink link:definitionLink 2417408 - Disclosure - Fair Value - Financial Instruments Not Carried at Fair Value (Details) link:presentationLink link:calculationLink link:definitionLink 2118106 - Disclosure - Investments link:presentationLink link:calculationLink link:definitionLink 2319304 - Disclosure - Investments (Tables) link:presentationLink link:calculationLink link:definitionLink 2420409 - Disclosure - Investments - Cost and Fair Value, Net of Credit Loss Allowance, of Available-For-Sale Securities (Details) link:presentationLink link:calculationLink link:definitionLink 2421410 - Disclosure - Investments - Amortized Cost and Estimated Fair Value of Available-For-Sale Securities by Contractual Maturity (Details) link:presentationLink link:calculationLink link:definitionLink 2422411 - Disclosure - Investments - Schedule of Available-For-Sale Securities in a Gross Unrealized Loss Position by Length of Time (Details) link:presentationLink link:calculationLink link:definitionLink 2423412 - Disclosure - Investments - Credit Loss Allowance on Investments (Details) link:presentationLink link:calculationLink link:definitionLink 2424413 - Disclosure - Investments - Schedule of Investment Income (Loss), Net of Expenses, from Portfolios (Details) link:presentationLink link:calculationLink link:definitionLink 2425414 - Disclosure - Investments - Realized and Unrealized Investment Gains (Losses) (Details) link:presentationLink link:calculationLink link:definitionLink 2426415 - Disclosure - Investments - Portion of Net Unrealized Gains and Losses Recognized During the Reporting Period Related To Equity Securities (Details) link:presentationLink link:calculationLink link:definitionLink 2427416 - Disclosure - Investments - Impairments on Available-For-Sale Securities (Details) link:presentationLink link:calculationLink link:definitionLink 2128107 - Disclosure - Borrowing Arrangements link:presentationLink link:calculationLink link:definitionLink 2429417 - Disclosure - Borrowing Arrangements - Term Loan Credit Facility (Details) link:presentationLink link:calculationLink link:definitionLink 2430418 - Disclosure - Borrowing Arrangements - Bank Line of Credit (Details) link:presentationLink link:calculationLink link:definitionLink 2131108 - Disclosure - Postretirement Benefits link:presentationLink link:calculationLink link:definitionLink 2332305 - Disclosure - Postretirement Benefits (Tables) link:presentationLink link:calculationLink link:definitionLink 2433419 - Disclosure - Postretirement Benefits (Details) link:presentationLink link:calculationLink link:definitionLink 2134109 - Disclosure - Income Taxes link:presentationLink link:calculationLink link:definitionLink 2435420 - Disclosure - Income Taxes (Details) link:presentationLink link:calculationLink link:definitionLink 2136110 - Disclosure - Capital Stock link:presentationLink link:calculationLink link:definitionLink 2437421 - Disclosure - Capital Stock - Class A and B Common Stock (Details) link:presentationLink link:calculationLink link:definitionLink 2438422 - Disclosure - Capital Stock - Stock Repurchases (Details) link:presentationLink link:calculationLink link:definitionLink 2139111 - Disclosure - Accumulated Other Comprehensive Income (Loss) link:presentationLink link:calculationLink link:definitionLink 2340306 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Tables) link:presentationLink link:calculationLink link:definitionLink 2441423 - Disclosure - Accumulated Other Comprehensive Income (Loss) (Details) link:presentationLink link:calculationLink link:definitionLink 2142112 - Disclosure - Concentrations of Credit Risk link:presentationLink link:calculationLink link:definitionLink 2443424 - Disclosure - Concentrations of Credit Risk (Details) link:presentationLink link:calculationLink link:definitionLink 2144113 - Disclosure - Commitments and Contingencies link:presentationLink link:calculationLink link:definitionLink 2445425 - Disclosure - Commitments and Contingencies (Details) link:presentationLink link:calculationLink link:definitionLink 2146114 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink