Net Income Per Share - Calculation of Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Earnings Per Share [Abstract]
Net income	$ 170,871	$ 149,213	$ 110,598	$ 75,749	$ 46,196	$ 89,915	$ 430,682	$ 211,860
Basic:
Weighted average shares (in shares)	110,176			112,809			110,816	112,953
Diluted:
Weighted average shares (in shares)	110,176			112,809			110,816	112,953
Dilutive effect of potential common shares (in shares)	1,314			546			1,138	491
Diluted weighted average shares (in shares)	111,490			113,355			111,954	113,444
Net income per share:
Basic (in usd per share)	$ 1.55			$ 0.67			$ 3.89	$ 1.88
Diluted (in usd per share)	$ 1.53			$ 0.67			$ 3.85	$ 1.87