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Fair value of company common stock

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Right To Elect Board Of Directors Percentage

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Share Based Compensation Arrangement By Share Based Payment Award Options Exercisable Number Year Three

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The weighted average price as of the end of the year at which grantees can acquire the shares reserved for issuance under the stock option plan which are not vested.

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Options outstanding exercisable now.

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Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Exercisable Year Five

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Options outstanding exercisable in year four.

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Options outstanding exercisable in year one.

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Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Number Exercisable Year Six

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Options outstanding exercisable in year three.

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Options outstanding exercisable in year two.

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The weighted average period between the balance sheet date and expiration for all awards outstanding but not vested under the plan, which may be expressed in a decimal value for number of years.

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Number of shares authorized to be repurchased remaining under previous authorization.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Aggregate number of common shares reserved for future issuance.

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Aggregate dividends declared during the period for each share of common stock outstanding.

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Aggregate carrying value as of the balance sheet date of the liabilities for stock option plans and other equity-based compensation arrangements.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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The cash outflow to reacquire common stock during the period.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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Gross number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of options outstanding, including both vested and non-vested options.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Number of non-vested options outstanding.

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Number of share options (or share units) exercised during the current period.

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Capital Stock, Stock Awards, and Stock Options (Narrative) (Details) - USD ($)	1 Months Ended	2 Months Ended	12 Months Ended
	Jan. 31, 2021	Feb. 24, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 10, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cost of shares repurchased by company			$ 161,829,000	$ 2,103,000	$ 118,030,000
Shares subject to award outstanding			27,240	29,140
Number of shares forfeited due to modification			1,650
Number of shares awarded in 2021			1,100
Exercised, Number of Shares			77,258
Number of shares granted			85,000
Stock options outstanding			190,931	183,189
Dividends declared per common share			$ 5.80	$ 5.56	$ 5.32
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares excluded from earnings per share					2,650
Kaplan Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercised, Number of Shares			0	0	0
Number of shares granted			0	0	0
Stock options outstanding			0
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares excluded from earnings per share			189,000	104,000	104,000
Maximum [Member] \| Kaplan Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			5 years
Minimum [Member] \| Kaplan Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Education [Member] \| Kaplan Stock Option and Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ (1,100,000)	$ (1,300,000)	$ 500,000
Accrual balance related to stock based compensation			9,000,000.0
Stock compensation payouts			$ 0	$ 0	$ 0
Class B Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Right to elect Board of Directors percentage			30.00%
Shares repurchased by company			406,112	3,392	199,023
Cost of shares repurchased by company			$ 161,800,000	$ 2,100,000	$ 118,000,000.0
Number of shares authorized to be repurchased						500,000
Number of shares authorized to be repurchased remaining under previous authorization						0
Authorized shares remaining for repurchase			364,151
Market value of company's stock			$ 533.38
Class B Common Stock [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share awards outstanding, restriction will lapse in 2021			12,575
Share awards outstanding, restriction will lapse in 2023			14,665
Stock-based compensation expense			$ 4,100,000	4,200,000	4,400,000
Total unrecognized compensation expense			$ 4,700,000
Years over which cost expected to be recognized			1 year 1 month 6 days
Class B Common Stock [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 2,200,000	$ 2,000,000.0	$ 2,000,000.0
Total unrecognized compensation expense			$ 8,100,000
Years over which cost expected to be recognized			5 years 4 months 24 days
Options outstanding exercisable now			100,804
Options outstanding exercisable in 2021			18,626
Options outstanding exercisable in 2022			14,500
Options outstanding exercisable in 2023			14,502
Options outstanding exercisable in 2024			14,167
Options outstanding exercisable in 2025			14,166
Options outstanding exercisable in 2026			14,166
Intrinsic value of options outstanding			$ 9,600,000
Intrinsic value of options exercisable			600,000
Intrinsic value of options unvested			$ 9,000,000.0
Options unvested, shares			90,127	22,461
Options unvested, average exercise price			$ 451.64	$ 780.81
Options unvested, weighted average remaining contractual term, years			9 years 4 months 24 days	5 years 4 months 24 days
Exercised, Number of Shares			77,258	1,743	588
Intrinsic value of options exercised			$ 11,100,000	$ 600,000	$ 200,000
Tax benefit from stock option exercises			$ 2,900,000	$ 200,000	$ 100,000
Class B Common Stock [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares awarded in 2021		19,293
Class B Common Stock [Member] \| 2012 Incentive Compensation Plan [Member] \| Share-based Payment Arrangement [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for stock awards granted under the plan			772,588
Shares reserved for issuance			557,871
Shares subject to award outstanding			218,171
Shares available for future awards			339,700
Class B Common Stock [Member] \| 2012 Incentive Compensation Plan [Member] \| 2020 Options Granted [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			6 years
Class B Common Stock [Member] \| 2012 Incentive Compensation Plan [Member] \| Maximum [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			10 years
Class B Common Stock [Member] \| 2012 Incentive Compensation Plan [Member] \| Minimum [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			6 years
Kaplan Restricted Stock [Member] \| Senior Manager [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares subject to award outstanding			7,206
Kaplan Restricted Stock [Member] \| Subsequent Event [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of company common stock	$ 1,247
Exercise Price Above Fair Market Value Of Common Stock [Member] \| Class B Common Stock [Member] \| Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted			85,000	0	0
Weighted average fair value, granted options			$ 93.79