Share-Based Compensation Plan (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Service Condition Restricted Share Activity

The following table provides a summary of service condition restricted share activity for the years ended December 31, 2023, 2022 and 2021:

	Shares	Weighted-Average Grant Date Fair Value
Unvested at January 1, 2021	242,727	$	24.94
Granted	415,531	$	22.69
Vested	(81,591)	$	30.41
Forfeited	(9,236)	$	23.37
Unvested at December 31, 2021	567,431	$	22.53
Granted	143,795	$	21.72
Vested	(107,303)	$	26.23
Forfeited	(36,606)	$	22.80
Unvested at December 31, 2022	567,317	$	21.60
Granted	113,084	$	15.04
Vested	(183,721)	$	23.14
Forfeited	(53,131)	$	16.72
Unvested at December 31, 2023	443,549	$	19.88

Schedule of Performance-Based Equity Awards, Fair Value Assumptions

The grant date fair value of the performance awards, with market conditions, were determined using a Monte Carlo simulation method with the following assumptions (dollars in millions):

Performance Award Grant Date		Percentage of Total Award	Grant Date Fair Value by Component	Volatility	Interest Rate	Dividend Yield
February 14, 2018
	Relative and Absolute Total Shareholder Return	65.00% / 35.00%	$3.5	28.00%	2.37%	4.70%
February 13, 2019
	Relative and Absolute Total Shareholder Return	65.00% / 35.00%	$4.5	26.00%	2.52%	4.20%
February 12, 2020
	Relative Total Shareholder Return	100.00%	$4.9	23.40%	1.41%	—%
February 18, 2021
	Relative Total Shareholder Return	100.00%	$6.0	56.00%	0.19%	—%
May 16, 2022
	Relative Total Shareholder Return	100.00%	$5.3	58.70%	2.72%	—%
February 17, 2023
	Relative and Absolute Total Shareholder Return	70.00% / 30.00%	$6.0	61.60%	4.31%	—%