Stock-Based Compensation - Summary of Stock-Based Compensation Grants (Detail)	6 Months Ended
	Jun. 30, 2020 $ / shares shares
Time Based Restricted Stock Units [Member]
Stock Awards Granted | shares	21,689
Weighted-Average Grant Price Per Share | $ / shares	$ 99.95
Performance Based Restricted Stock Units [Member]
Stock Awards Granted | shares	38,842	[1]
Weighted-Average Grant Price Per Share | $ / shares	$ 78.64	[1]
Stock Appreciation Rights [Member]
Stock Awards Granted | shares	21,643
Weighted-Average Grant Price Per Share | $ / shares	$ 100.30

[1] Includes 26,652 of target performance-based restricted stock unit awards granted during the six months ended June 30, 2020, and adjustments of (2,562), 3,029 and 11,723 to grants due to the actual performance level achieved for restricted stock and restricted stock units awarded in 2019, 2018, and 2017, respectively.