Stock-Based Compensation - Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stock-based compensation
Stock-based compensation expense	$ 9.6	$ 10.3	$ 13.1
Related income tax benefit of stock-based compensation	$ 2.3	$ 2.5	$ 3.1
Employee stock-based compensation plan
Stock-based compensation
Total shares authorized	5,600,000
Shares available for future grants	2,500,000
Non-employee director plan
Stock-based compensation
Total shares authorized	268,941
Shares available for future grants	128,434