Stock-Based Compensation Plans - Full Value Awards activity (Detail) - Restricted Stock [Member] - $ / shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Restricted Shares, Beginning balance	199,801	160,544	162,356
Number of Restricted Shares, Granted	203,579	150,031	90,242
Number of Restricted Shares, Performance share pay-out	9,812	4,739	12,145
Number of Restricted Shares, Forfeited	(30,645)	(29,581)	(5,272)
Number of Restricted Shares, Vested	(107,995)	(85,932)	(98,927)
Number of Restricted Shares, Ending balance	274,552	199,801	160,544
Weighted Average Grant Date Fair Value, Beginning balance	$ 276.74	$ 346.15	$ 321.04
Weighted Average Grant Date Fair Value, Granted	194.2	217.8	328.17
Weighted Average Grant Date Fair Value, Performance share pay-out	350.94	522.57	360.9
Weighted Average Grant Date Fair Value, Forfeited	226.61	255.35	376.51
Weighted Average Grant Date Fair Value, Vested	278.22	324.42	288.73
Weighted Average Grant Date Fair Value, Ending balance	$ 223.2	$ 276.74	$ 346.15