Capital Stock, Stock Awards, and Stock Options (Narrative) (Details) - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Sep. 10, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cost of shares repurchased by company		$ 55,683,000	$ 161,829,000	$ 2,103,000
Shares subject to award outstanding		31,571	27,240
Number of shares forfeited due to modification		3,056
Number of shares awarded in 2021		20,258
Exercised, Number of Shares		0
Number of shares granted		0
Stock options outstanding		183,189	183,189
Dividends declared per common share		$ 6.04	$ 5.80	$ 5.56
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		104,000	181,258	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 (credit)		$ 1,300,000	$ (1,100,000)	$ (1,300,000)
Accrual balance related to stock based compensation		10,300,000
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		93,969	406,112	3,392
Cost of shares repurchased by company		$ 55,700,000	$ 161,800,000	$ 2,100,000
Number of shares authorized to be repurchased					500,000
Authorized shares remaining for repurchase		270,182
Market value of company's stock (in dollars per share)		$ 629.83
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 2023		12,820
Share awards outstanding, restriction will lapse in 2025		16,751
Share awards outstanding, restriction will lapse in 2027		2,000
Stock-based compensation expense (credit)		$ 3,900,000	4,100,000	4,200,000
Total unrecognized compensation expense		$ 9,800,000
Years over which cost expected to be recognized		2 years 3 months 18 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 (credit)		$ 1,700,000	$ 2,200,000	$ 2,000,000
Total unrecognized compensation expense		$ 5,700,000
Years over which cost expected to be recognized		4 years 8 months 12 days
Options outstanding exercisable now		118,139
Options outstanding exercisable in 2022 (shares)		13,209
Options outstanding exercisable in 2023 (shares)		13,211
Options outstanding exercisable in 2024 (shares)		12,876
Options outstanding exercisable in 2025 (shares)		12,877
Options outstanding exercisable in 2026 (shares)		12,877
Intrinsic value of options outstanding		$ 16,400,000
Intrinsic value of options exercisable		3,400,000
Intrinsic value of options unvested		$ 13,100,000
Options unvested, shares		65,050	82,385
Options unvested, average exercise price (in dollars per share)		$ 431.16	$ 453.97
Options unvested, weighted average remaining contractual term, years		8 years 8 months 12 days	9 years 4 months 24 days
Exercised, Number of Shares		0	77,258	1,743
Intrinsic value of options exercised			$ 11,100,000	$ 600,000
Tax benefit from stock option exercises			$ 2,900,000	$ 200,000
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		545,000
Shares subject to award outstanding		214,760
Shares available for future awards		330,240
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 (in dollars per share)	$ 1,425
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		0	77,258	0
Weighted average fair value, granted options (in dollars per share)			$ 93.79