Equity Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement, Noncash Expense [Abstract]

Weighted Average Assumptions Used to Estimate Fair Value of Stock Options

The fair value of stock options was estimated on the date of grant using the Black-Scholes option pricing model with the following weighted average assumptions used for grants:

	2021			2020			2019
Stock price	$	329.71		$	244.74		$	304.85
Risk-free interest rates	1.22		%	0.83		%	2.01		%
Expected lives	6 years			6 years			6 years
Volatility	27.00		%	25.72		%	19.56		%
Dividend yield	2.90		%	2.93		%	2.72		%

Summary of Stock Options Activity

A summary of the status of the Company’s stock option plans as of December 31, 2021, 2020, and 2019 and changes during the years ended on those dates is presented below:

	2021			2020			2019
	Shares	Weighted- average exercise price		Shares	Weighted- average exercise price		Shares	Weighted- average exercise price
Outstanding at beginning of year	613,109	$	255.86	572,971	$	251.10	612,954	$	224.57
Granted	99,479	329.71		149,020	244.74		148,147	304.85
Exercised	(248,725)	231.37		(70,802)	208.57		(182,817)	205.25
Forfeited and canceled	—	—		(38,080)	228.64		(5,313)	257.87
Outstanding at end of year	463,863	284.82		613,109	255.86		572,971	251.10
Options exercisable at year end	274,244	270.11		361,985	245.83		305,379	223.90

Summary of Restricted Stock Activity

The following table summarizes information about restricted stock outstanding as of December 31, 2021, 2020 and 2019 and changes during the years ended:

	2021			2020			2019
	Shares	Weighted- average grant price		Shares	Weighted- average grant price		Shares	Weighted- average grant price
Unvested at beginning of year	132,603	$	214.34	114,877	$	197.62	91,058	$	180.99
Granted	50,349	337.52		45,196	248.16		41,643	235.93
Vested	(22,387)	229.90		(15,116)	170.61		(13,222)	143.56
Forfeited and canceled	(1,164)	219.30		(12,354)	184.11		(4,602)	158.06
Unvested at end of year	159,401	251.03		132,603	214.34		114,877	197.62

Summary of Long Term Incentive Plan - Z Units

The following table summarizes information about the LTIP Units outstanding as of December 31, 2021:

	Long-Term Incentive Plan - LTIP Units
	Total Vested Units	Total Unvested Units	Total Outstanding Units	Weighted- average Grant-date Fair Value		Weighted- average Remaining Contractual Life (years)
Balance, December 31, 2018	134,081	11,161	145,242	$	75.03	6.5
Granted	—	—	—
Vested	9,176	(9,176)	—
Converted	—	—	—
Cancelled	—	(95)	(95)
Balance, December 31, 2019	143,257	1,890	145,147	$	75.03	5.2
Granted	—	—	—
Vested	1,890	(1,890)	—
Converted	(39,010)	—	(39,010)
Cancelled	—	—	—
Balance, December 31, 2020	106,137	—	106,137	$	84.47	3.6
Granted	—	—	—
Vested	—	—	—
Converted	—	—	—
Cancelled	—	—	—
Balance, December 31, 2021	106,137	—	106,137	$	84.47	2.6