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Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Oct. 31, 2018	May 24, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Number of shares of common stock subject to awards					1,500,000
Shares available for grant	1,300,115	1,361,748	1,570,274
Weighted average diluted shares outstanding excludes shares of common stock subject to stock options	110,900	122,775	94,747
Number of shares authorized to be repurchased (in shares)				150,000,000.0
Stock repurchase program, period in force	3 years
Stock repurchased during period (in shares)	402,570		402,570,000
Weighted average price (in usd per share)	$ 71.28
Stock repurchased during period	$ 28,700		$ 28,695
Deferred and Restricted Stock Unit
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation costs	$ 17,000
Unrecognized compensation costs, weighted-average recognition period	1 year 2 months 12 days
Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation costs	$ 5,200
Unrecognized compensation costs, weighted-average recognition period	10 months 24 days