Common Stock (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common stock repurchases, value	$ 50,347	$ 138,275	$ 40,791
Common Stock
Class of Stock [Line Items]
Treasury shares issued (in shares)	0	0	0
Employee stock plans (in shares)	505,623	332,893	341,837
Treasury Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)	900,000	2,292,100	677,100
Common stock repurchases, value	$ 50,347	$ 138,275	$ 40,791
Employee stock plans (in shares)	117,000	86,000	89,000