Share-Based Compensation and Capital Stock - Pre-Tax Stock-Based Compensation Expenses And Associated Income Tax Benefits (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ 3,378	$ 4,005	$ 2,891	$ 11,765
Income tax benefits	805	964	689	2,831
Stock options
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	497	541	1,478	1,667
Restricted stock
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	2,206	1,954	6,249	6,100
Performance Vested Restricted Stock Units
Share-Based Compensation and Capital Stock [Line Items]
Share-based compensation expense	$ 675	$ 1,510	$ (4,836)	$ 3,998