Stock Plans and Management Compensation (Tables)

12 Months Ended

Dec. 31, 2022

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 $93.62, $91.14 and $64.13 for units granted in 2022, 2021 and 2020, respectively. Non-vested stock unit activity for the year ended December 31, 2022 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, 2022	635	66.81
Awarded	226	93.62
Forfeited	(28)	83.15
Vested	(232)	51.32
Non-vested units, unvested as of December 31, 2022	601	82.14

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 2022, 2021 and 2020 were $94.59, $91.44 and $64.72, respectively, which were estimated using the Monte Carlo valuation model, and incorporated the following assumptions:

	2022		2021		2020
Risk-free interest rate	1.7	%	0.2	%	1.4	%
Dividend yield	1.5	%	1.2	%	1.5	%
Volatility factor	54.8	%	65.6	%	46.6	%
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, 2022 was as follows:

(in thousands, except grant date fair value)	Performance Awards	Weighted Average Grant Date Fair Value ($)
Performance awards, unvested at January 1	192	76.15
Awarded	207	70.32
Forfeited	(5)	81.31
Vested and earned	(203)	56.11
Performance awards, unvested at December 31	191	90.97