Accounting Policies - Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Net income	$ 454,627	$ 433,887	$ 451,295
Weighted average shares outstanding - basic	87,100	85,840	84,259
Dilutive effect of stock plans	1,002	1,448	1,666
Weighted average shares outstanding - diluted	88,102	87,288	85,925
Basic earnings per share	$ 5.22	$ 5.05	$ 5.36
Diluted earnings per share	$ 5.16	$ 4.97	$ 5.25
Anti-dilutive shares	23	23	14