Common Stock (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock repurchases, value	$ 15,550	$ 50,347	$ 138,275
Common Stock
Class of Stock [Line Items]
Treasury shares issued (in shares)	0	0	0
Employee stock plans (in shares)	298,565	505,623	332,893
Treasury Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)	396,000	900,000	2,292,100
Common stock repurchases, value	$ 15,550	$ 50,347	$ 138,275
Employee stock plans (in shares)	83,000	117,000	86,000