Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Nonvested Restricted Stock Units and Changes During the Period

Nonvested restricted stock units as of June 30, 2022, and changes during the six months ended June 30, 2022 (unaudited) were as follows:

	Shares			Weighted Average Grant-Date Fair Value
Nonvested as of December 31, 2021		355,434		$	34.40
Granted		136,111			30.76
Vested		(37,235	)		33.61
Forfeited		(5,155	)		34.48
Nonvested as of June 30, 2022		449,155		$	33.36

Schedule of Stock-Based Compensation Expense

The Company's stock-based compensation expense related to the restricted stock units during the three and six months ended June 30, 2022 and 2021 (unaudited), respectively, which was included in General and administrative expenses within the Condensed Consolidated Statements of Income, was as follows:

	Three Months Ended				Six Months Ended
(millions)	June 30, 2022		June 30, 2021		June 30, 2022		June 30, 2021
Stock-based compensation expense	$	1.5	$	1.3	$	2.8	$	2.1

The Company's stock-based compensation expense related to PSUs during the three and six months ended June 30, 2022 and 2021 (unaudited), which is included in General and administrative expenses within the Condensed Consolidated Statements of Income, was as follows:

	Three Months Ended				Six Months Ended
(millions)	June 30, 2022		June 30, 2021		June 30, 2022		June 30, 2021
Stock-based compensation expense	$	0.7	$	0.3	$	1.2	$	0.4

Summary of Nonvested PSU's and Changes During the Period

Nonvested PSUs as of June 30, 2022, and changes during the three and six months ended June 30, 2022 (unaudited) were as follows:

	Shares			Weighted Average Grant-Date Fair Value
Nonvested as of December 31, 2021		135,383		$	36.79
Granted		132,304			30.80
Forfeited		(2,660	)		36.91
Nonvested as of June 30, 2022		265,027		$	33.80