Computation of Earnings Per Share - Calculations Of Basic And Diluted (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Numerator:
Net income used for calculating basic and diluted income per share	$ 164,100	$ 75,097
Denominator:
Weighted average number of common shares used in the calculation of basic income per share (in shares)	88,352	89,219
Dilutive effect of outstanding awards associated with stock-based compensation plans (in shares)	787	847
Shares used in the calculation of diluted income per share (in shares)	89,139	90,066
Basic income per share (in dollars per share)	$ 1.86	$ 0.84
Diluted income per share (in dollars per share)	$ 1.84	$ 0.83