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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 One

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

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

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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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Options outstanding exercisable in year three.

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Options outstanding exercisable in year two.

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Share Based Compensation Arrangement By Share Based Payment Award Options Unvested Intrinsic Value

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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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Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

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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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Amount of distribution made to individual in accordance with deferred compensation arrangement.

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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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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of tax benefit from exercise of stock options granted under share-based compensation arrangement.

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The cash outflow to reacquire common stock during the period.

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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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, 2019	Feb. 25, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Nov. 09, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cost of shares repurchased by company			$ 118,030,000	$ 50,770,000	$ 108,948,000
Shares subject to award outstanding			32,200	51,575
Number of shares forfeited due to modification			5,475
Number of shares awarded in 2019			375
Exercised, Number of Shares			588
Number of shares granted			0
Stock options outstanding			184,932	185,520
Dividends declared per common share			$ 5.32	$ 5.08	$ 4.84
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares excluded from earnings per share			2,650	5,250	5,450
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
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares excluded from earnings per share			104,000	104,000	102,000
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			$ 500,000	$ 1,200,000	$ 600,000
Accrual balance related to stock based compensation			11,300,000
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			199,023	88,361	229,498
Cost of shares repurchased by company			$ 118,000,000	$ 50,800,000	$ 108,900,000
Number of shares authorized to be repurchased						500,000
Number of shares authorized to be repurchased remaining under previous authorization						163,237
Authorized shares remaining for repurchase			273,655
Market value of company's stock			$ 640.58
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 2019			18,500
Share awards outstanding, restriction will lapse in 2020			250
Share awards outstanding, restriction will lapse in 2021			13,450
Stock-based compensation expense			$ 4,400,000	8,100,000	11,000,000
Total unrecognized compensation expense			$ 3,600,000
Years over which cost expected to be recognized			11 months 4 days
Class B Common Stock [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense			$ 2,000,000	$ 2,000,000	$ 2,400,000
Total unrecognized compensation expense			$ 4,400,000
Years over which cost expected to be recognized			2 years 3 months 18 days
Options outstanding exercisable now			145,138
Options outstanding exercisable in 2019			17,333
Options outstanding exercisable in 2020			17,334
Options outstanding exercisable in 2021			4,459
Options outstanding exercisable in 2022			333
Options outstanding exercisable in 2023			335
Intrinsic value of options outstanding			$ 25,800,000
Intrinsic value of options exercisable			25,800,000
Intrinsic value of options unvested			$ 0
Options unvested, shares			39,794	57,126
Options unvested, average exercise price			$ 770.29	$ 770.67
Options unvested, weighted average remaining contractual term, years			6 years 3 months 18 days	7 years 2 months 12 days
Exercised, Number of Shares			588	3,476	4,726
Intrinsic value of options exercised			$ 200,000	$ 700,000	$ 1,200,000
Tax benefit from stock option exercises			$ 100,000	$ 300,000	$ 500,000
Weighted average fair value, granted options				$ 120.47
Class B Common Stock [Member] \| Subsequent Event [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares awarded in 2019		16,665
Class B Common Stock [Member] \| 2003 Employee Stock Option Plan [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for stock awards granted under the plan			1,900,000
Shares reserved for issuance			79,001
Class B Common Stock [Member] \| 2003 Employee Stock Option Plan [Member] \| Maximum [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			10 years
Class B Common Stock [Member] \| 2003 Employee Stock Option Plan [Member] \| Minimum [Member] \| Employee Stock Option [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] \| Stock Compensation Plan [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			575,208
Shares subject to award outstanding			138,131
Shares available for future awards			437,077
Class B Common Stock [Member] \| 2012 Incentive Compensation Plan [Member] \| 2017 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] \| Employee Stock 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] \| Employee Stock 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	$ 1,575
Exercise Price Above Fair Market Value Of Common Stock [Member] \| Class B Common Stock [Member] \| Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares granted			0	2,000	0