Significant Accounting Policies (Policies)	3 Months Ended
Mar. 31, 2021
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. For further information, refer to the financial statements and footnotes included in our Form 10-K for the year ended December 31, 2020 as filed with the Securities and Exchange Commission on February 25, 2021.
Use of estimates	Use of estimates The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Reclassifications	ReclassificationsCertain amounts previously reported have been reclassified for comparative purposes to conform to the current period’s presentation. "Federal income taxes recoverable" is now included in "Prepaid expenses and other current assets" in the Statements of Financial Position. “Equity in earnings (losses) of limited partnerships” is now included in “Net investment income” in the Statements of Operations. The reclassifications had no effect on previously reported net income.
Earnings per share	Class A and Class B basic earnings per share and Class B diluted earnings per share are calculated under the two-class method. The two-class method allocates earnings to each class of stock based upon its dividend rights. Class B shares are convertible into Class A shares at a conversion ratio of 2,400 to 1. See Note 10, "Capital Stock".Class A diluted earnings per share are calculated under the if-converted method, which reflects the conversion of Class B shares to Class A shares. Diluted earnings per share calculations include the dilutive effect of assumed issuance of stock-based awards under compensation plans that have the option to be paid in stock using the treasury stock method.
Financial instruments carried at fair value	Financial instruments carried at fair value Our available-for-sale and equity securities are recorded at fair value, which is the price that would be received to sell the asset in an orderly transaction between willing market participants as of the measurement date. Valuation techniques used to derive the fair value of our available-for-sale and equity securities are based upon observable and unobservable inputs. Observable inputs reflect market data obtained from independent sources. Unobservable inputs reflect our own assumptions regarding fair market value for these securities. Financial instruments are categorized based upon the following characteristics or inputs to the valuation techniques: •Level 1 – Quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date. •Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly. •Level 3 – Unobservable inputs for the asset or liability. Estimates of fair values for our investment portfolio are obtained primarily from a nationally recognized pricing service. Our Level 1 securities are valued using an exchange traded price provided by the pricing service. Pricing service valuations for Level 2 securities include multiple verifiable, observable inputs including benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data. Pricing service valuations for Level 3 securities are based upon proprietary models and are used when observable inputs are not available or in illiquid markets. Although virtually all of our prices are obtained from third party sources, we also perform internal pricing reviews, including evaluating the methodology and inputs used to ensure that we determine the proper classification level of the financial instrument and reviewing securities with price changes that vary significantly from current market conditions or independent price sources. Price variances are investigated and corroborated by market data and transaction volumes. We have reviewed the pricing methodologies of our pricing service as well as other observable inputs and believe that the prices adequately consider market activity in determining fair value. In limited circumstances we adjust the price received from the pricing service when, in our judgment, a better reflection of fair value is available based upon corroborating information and our knowledge and monitoring of market conditions such as a disparity in price of comparable securities and/or non-binding broker quotes. In other circumstances, certain securities are internally priced because prices are not provided by the pricing service. When a price from the pricing service is not available, values are determined by obtaining broker/dealer quotes and/or market comparables. When available, we obtain multiple quotes for the same security. The ultimate value for these securities is determined based upon our best estimate of fair value using corroborating market information. As of March 31, 2021, nearly all of our available-for-sale and equity securities were priced using a third party pricing service.
Fair value of financial statements, transfers between levels	We review the fair value hierarchy classifications each reporting period. Transfers between hierarchy levels may occur due to changes in available market observable inputs.
Commitments and contingencies	We are involved in litigation arising in the ordinary course of conducting business. In accordance with current accounting standards for loss contingencies and based upon information currently known to us, we establish reserves for litigation when it is probable that a loss associated with a claim or proceeding has been incurred and the amount of the loss or range of loss can be reasonably estimated. When no amount within the range of loss is a better estimate than any other amount, we accrue the minimum amount of the estimable loss. To the extent that such litigation against us may have an exposure to a loss in excess of the amount we have accrued, we believe that such excess would not be material to our financial condition, results of operations, or cash flows. Legal fees are expensed as incurred. We believe that our accruals for legal proceedings are appropriate and, individually and in the aggregate, are not expected to be material to our financial condition, results of operations, or cash flows. We review all litigation on an ongoing basis when making accrual and disclosure decisions. For certain legal proceedings, we cannot reasonably estimate losses or a range of loss, if any, particularly for proceedings that are in their early stages of development or where the plaintiffs seek indeterminate damages. Various factors, including, but not limited to, the outcome of potentially lengthy discovery and the resolution of important factual questions, may need to be determined before probability can be established or before a loss or range of loss can be reasonably estimated. If the loss contingency in question is not both probable and reasonably estimable, we do not establish an accrual and the matter will continue to be monitored for any developments that would make the loss contingency both probable and reasonably estimable. In the event that a legal proceeding results in a substantial judgment against, or settlement by, us, there can be no assurance that any resulting liability or financial commitment would not have a material adverse effect on the financial condition, results of operations, or cash flows.

Significant Accounting Policies (Policies)

3 Months Ended

Mar. 31, 2021

The accompanying unaudited financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America ("GAAP") for interim financial information and the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they do not include all the information and footnotes required by GAAP for complete financial statements. In the opinion of management, all adjustments (consisting of normal recurring accruals) considered necessary for a fair presentation have been included. Operating results for the three months ended March 31, 2021 are not necessarily indicative of the results that may be expected for the year ending December 31, 2021. For further information, refer to the financial statements and footnotes included in our Form 10-K for the year ended December 31, 2020 as filed with the Securities and Exchange Commission on February 25, 2021.

Use of estimates

The preparation of financial statements in conformity with GAAP requires us to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.

Reclassifications

ReclassificationsCertain amounts previously reported have been reclassified for comparative purposes to conform to the current period’s presentation. "Federal income taxes recoverable" is now included in "Prepaid expenses and other current assets" in the Statements of Financial Position. “Equity in earnings (losses) of limited partnerships” is now included in “Net investment income” in the Statements of Operations. The reclassifications had no effect on previously reported net income.

Earnings per share

Class A and Class B basic earnings per share and Class B diluted earnings per share are calculated under the two-class method. The two-class method allocates earnings to each class of stock based upon its dividend rights. Class B shares are convertible into Class A shares at a conversion ratio of 2,400 to 1. See Note 10, "Capital Stock".Class A diluted earnings per share are calculated under the if-converted method, which reflects the conversion of Class B shares to Class A shares. Diluted earnings per share calculations include the dilutive effect of assumed issuance of stock-based awards under compensation plans that have the option to be paid in stock using the treasury stock method.

Financial instruments carried at fair value

Our available-for-sale and equity securities are recorded at fair value, which is the price that would be received to sell the asset in an orderly transaction between willing market participants as of the measurement date.

Valuation techniques used to derive the fair value of our available-for-sale and equity securities are based upon observable and unobservable inputs. Observable inputs reflect market data obtained from independent sources. Unobservable inputs reflect our own assumptions regarding fair market value for these securities. Financial instruments are categorized based upon the following characteristics or inputs to the valuation techniques:

•Level 1 – Quoted prices (unadjusted) in active markets for identical assets or liabilities that the reporting entity can access at the measurement date.

•Level 2 – Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly.

•Level 3 – Unobservable inputs for the asset or liability.

Estimates of fair values for our investment portfolio are obtained primarily from a nationally recognized pricing service. Our Level 1 securities are valued using an exchange traded price provided by the pricing service. Pricing service valuations for Level 2 securities include multiple verifiable, observable inputs including benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers, and reference data. Pricing service valuations for Level 3 securities are based upon proprietary models and are used when observable inputs are not available or in illiquid markets.

Although virtually all of our prices are obtained from third party sources, we also perform internal pricing reviews, including evaluating the methodology and inputs used to ensure that we determine the proper classification level of the financial instrument and reviewing securities with price changes that vary significantly from current market conditions or independent price sources. Price variances are investigated and corroborated by market data and transaction volumes. We have reviewed the pricing methodologies of our pricing service as well as other observable inputs and believe that the prices adequately consider market activity in determining fair value.

In limited circumstances we adjust the price received from the pricing service when, in our judgment, a better reflection of fair value is available based upon corroborating information and our knowledge and monitoring of market conditions such as a disparity in price of comparable securities and/or non-binding broker quotes. In other circumstances, certain securities are internally priced because prices are not provided by the pricing service.

When a price from the pricing service is not available, values are determined by obtaining broker/dealer quotes and/or market comparables. When available, we obtain multiple quotes for the same security. The ultimate value for these securities is determined based upon our best estimate of fair value using corroborating market information. As of March 31, 2021, nearly all of our available-for-sale and equity securities were priced using a third party pricing service.

Fair value of financial statements, transfers between levels

We review the fair value hierarchy classifications each reporting period. Transfers between hierarchy levels may occur due to changes in available market observable inputs.

Commitments and contingencies

We are involved in litigation arising in the ordinary course of conducting business. In accordance with current accounting standards for loss contingencies and based upon information currently known to us, we establish reserves for litigation when it is probable that a loss associated with a claim or proceeding has been incurred and the amount of the loss or range of loss can be reasonably estimated. When no amount within the range of loss is a better estimate than any other amount, we accrue the minimum amount of the estimable loss. To the extent that such litigation against us may have an exposure to a loss in excess of the amount we have accrued, we believe that such excess would not be material to our financial condition, results of operations, or cash flows. Legal fees are expensed as incurred. We believe that our accruals for legal proceedings are appropriate and, individually and in the aggregate, are not expected to be material to our financial condition, results of operations, or cash flows.

We review all litigation on an ongoing basis when making accrual and disclosure decisions. For certain legal proceedings, we cannot reasonably estimate losses or a range of loss, if any, particularly for proceedings that are in their early stages of development or where the plaintiffs seek indeterminate damages. Various factors, including, but not limited to, the outcome of potentially lengthy discovery and the resolution of important factual questions, may need to be determined before probability can be established or before a loss or range of loss can be reasonably estimated. If the loss contingency in question is not both probable and reasonably estimable, we do not establish an accrual and the matter will continue to be monitored for any developments that would make the loss contingency both probable and reasonably estimable. In the event that a legal proceeding results in a substantial judgment against, or settlement by, us, there can be no assurance that any resulting liability or financial commitment would not have a material adverse effect on the financial condition, results of operations, or cash flows.