Stock Plans and Management Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement, Noncash Expense [Abstract]

Non-Vested Stock Award Activity

The weighted average price per non-vested stock unit at grant date was $88.00, $93.62 and $91.14 for units granted in 2023, 2022 and 2021, respectively. Non-vested stock unit activity for the year ended December 31, 2023 was as follows:

(in thousands, except grant date fair value)	Non-vested Stock Unit Activity	Weighted Average Grant Date Fair Value ($)
Non-vested units, unvested as of January 1, 2023	601	82.14
Awarded	278	88.00
Forfeited	(49)	86.54
Vested	(253)	68.17
Non-vested units, unvested as of December 31, 2023	577	90.72

Fair Value Assumptions for Performance Awards

The fair values of the senior executives' performance share award grants with a TSR modifier at the grant date in 2023, 2022 and 2021 were $88.47, $94.59 and $91.44, respectively, which were estimated using the Monte Carlo valuation model, and incorporated the following assumptions:

	2023		2022		2021
Risk-free interest rate	4.3	%	1.7	%	0.2	%
Dividend yield	1.8	%	1.5	%	1.2	%
Volatility factor	49.8	%	54.8	%	65.6	%
Expected life of award	2.9 years		2.9 years		2.9 years

Performance Award Activity

Performance award activity for the year ended December 31, 2023 was as follows:

(in thousands, except grant date fair value)	Performance Awards	Weighted Average Grant Date Fair Value ($)
Performance awards, unvested at January 1	191	90.97
Awarded	206	78.49
Forfeited	(13)	87.15
Vested and earned	(167)	77.02
Performance awards, unvested at December 31	217	90.09