Stock-Based Compensation - Summary of Stock-Based Compensation Grants (Detail)	9 Months Ended
	Sep. 30, 2021 $ / shares shares
Time Based Restricted Stock Units [Member]
Stock Awards Granted | shares	33,442
Weighted-Average Grant Price Per Share | $ / shares	$ 101.28
Performance Based Restricted Stock Units [Member]
Stock Awards Granted | shares	36,522	[1]
Weighted-Average Grant Price Per Share | $ / shares	$ 86.26	[1]
Stock Appreciation Rights [Member]
Stock Awards Granted | shares	15,029
Weighted-Average Grant Price Per Share | $ / shares	$ 104.56

[1] Includes 26,511 of target performance-based restricted stock unit awards granted during the nine months ended September 30, 2021, and adjustments of 4,813, (887) and 6,085 to grants due to the actual performance level achieved for restricted stock and restricted stock units awarded in 2020, 2019, and 2018, respectively.