Stock-based compensation plans (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Restricted Stock and Restricted Stock Unit Activity

A summary of restricted stock and restricted stock unit activity follows:

	Restricted Stock Units Outstanding			Weighted- Average Grant Price		Restricted Stock Outstanding			Weighted- Average Grant Price
Unvested at January 1, 2023		1,167,582		$	156.23		75,006		$	164.65
Granted		752,534			153.86		—			—
Vested		(543,987	)		156.97		(35,777	)		164.66
Cancelled		(45,851	)		159.73		(7,514	)		164.66
Unvested at December 31, 2023		1,330,278		$	154.46		31,715		$	164.63

Summary of Stock Option Activity

A summary of stock option activity follows:

				Weighted-Average
	Stock Options Outstanding			Exercise Price		Life (In Years)		Aggregate Intrinsic Value (In millions)
Outstanding at January 1, 2023		2,340,062		$	148.78
Granted		179,551			156.00
Exercised		(262,837	)		122.45
Expired		(58,112	)		155.87
Outstanding at December 31, 2023		2,198,664		$	152.33		5.6	$	6
Exercisable at December 31, 2023		1,807,515		$	151.67		5.0	$	5