Net Income Per Share - Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator:
Net income	$ 196,888	$ 144,793	$ 377,254	$ 283,224
Denominator:
Weighted-average shares used in computing net income per share, basic (in shares)	76,461	75,808	76,384	76,036
Add weighted-average effect of dilutive securities:
Stock options and RSUs (in shares)	3,191	3,486	3,235	3,580
Employee stock purchase plan (in shares)	58	4	58	4
Weighted-average shares used in computing net income per share, diluted (in shares)	79,710	79,298	79,677	79,620
Net income per share:
Basic (in dollars per share)	$ 2.58	$ 1.91	$ 4.94	$ 3.72
Diluted (in dollars per share)	$ 2.47	$ 1.83	$ 4.73	$ 3.56