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				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net income used for calculating basic and diluted income per share	$ 271,236	$ 164,100	$ 55,077	$ 75,097	$ 435,336	$ 130,174
Denominator:
Weighted average number of common shares used in the calculation of basic income per share (in shares)	85,712		89,323		87,032	89,271
Dilutive effect of outstanding awards associated with stock-based compensation plans (in shares)	877		457		889	696
Shares used in the calculation of diluted income per share (in shares)	86,589		89,780		87,921	89,967
Basic income per share (in dollars per share)	$ 3.16		$ 0.62		$ 5.00	$ 1.46
Diluted income per share (in dollars per share)	$ 3.13		$ 0.61		$ 4.95	$ 1.45