Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Net Income	$ 98,655	$ 30,912
Weighted average shares outstanding: [Abstract]
Basic (in shares)	40,215	40,125
Effect of dilutive securities: [Abstract]
Stock options and employee stock purchase plan (in shares)	631	830
Diluted (in shares)	40,846	40,955
Earnings Per Share, Basic and Diluted [Abstract]
Basic (in dollars per share)	$ 2.45	$ 0.77
Diluted (in dollars per share)	$ 2.42	$ 0.75
Anti-dilutive stock options excluded from diluted earnings per share computations (in shares)	0	66