Equity - Narrative (Details)			3 Months Ended	12 Months Ended
	Dec. 31, 2022 USD ($) $ / shares shares	May 27, 2021 USD ($)	Jun. 30, 2020 USD ($) shares	Dec. 31, 2022 USD ($) classOfCommonStockOutstanding $ / shares shares	Dec. 30, 2022 shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Mar. 31, 2021 USD ($)	Dec. 31, 2019 shares	Mar. 14, 2019 USD ($)	Sep. 30, 2015 USD ($)
Class of Stock [Line Items]
Number of classes of common stock outstanding | classOfCommonStockOutstanding				3
Quarterly dividend on all classes of common stock (in dollars per share) | $ / shares				$ 0.95		$ 0.88	$ 0.80
Share expiration period				10 years
SARs exercise price (in dollars per share) | $ / shares				$ 120.38		$ 88.68
Excess tax benefits related to stock-based awards				$ 101,000		$ 292,000	$ (440,000)
Decrease in additional paid-in capital				(1,900,000)		(1,300,000)	(600,000)
Intrinsic value of outstanding, exercisable and vested or excepted to vest restricted stock	$ 16,300,000			16,300,000		20,400,000
Intrinsic value of shares exercised				1,100,000		$ 900,000	$ 700,000
Unrecognized compensation cost	3,700,000			$ 3,700,000
Weighted-average period of recognition				1 year 8 months 12 days
Weighted-average grant date fair value (in dollars per share) | $ / shares				$ 91.94		$ 65.48	$ 45.91
Compensation expense				$ 4,600,000		$ 4,300,000	$ 4,100,000
Granted (in dollars per share) | $ / shares				$ 120.14		$ 88.92	$ 66.02
Capital required for capital adequacy	805,900,000			$ 805,900,000		$ 713,100,000
Capital	1,300,000,000			1,300,000,000		1,200,000,000
Excess capital	$ 516,900,000			$ 516,900,000		496,800,000
Outstanding, SARs (in shares) | shares	132,163			132,163
Stock Appreciation Rights (SARs)
Class of Stock [Line Items]
Tax benefit from exercise of SARs				$ 1,200,000		$ 900,000	$ 500,000
Outstanding, SARs (in shares) | shares	132,163			132,163		130,409	116,417		98,836
Minimum
Class of Stock [Line Items]
SARs exercise price (in dollars per share) | $ / shares							$ 72.26
Minimum | Restricted Stock
Class of Stock [Line Items]
Vesting period				1 year		1 year	1 year
Maximum
Class of Stock [Line Items]
SARs exercise price (in dollars per share) | $ / shares							$ 75.16
Maximum | Restricted Stock
Class of Stock [Line Items]
Vesting period				3 years		3 years	3 years
Series G
Class of Stock [Line Items]
Preferred stock, dividend rate		4.875%		4.875%		4.875%
Preferred stock, par value (in dollars per share) | $ / shares	$ 25			$ 25		$ 25
Payments of stock issuance costs		$ 3,661,677
Class C non-voting common stock
Class of Stock [Line Items]
Stock authorized for repurchase										$ 10,000,000	$ 25,000,000
Shares repurchased (in shares) | shares	673,000		4,000		0
Shares repurchased	$ 19,800,000		$ 200,000
Remaining authorized amount for repurchase								$ 9,800,000