Net Income Per Share - Calculation of Net Income 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	$ 110,598	$ 89,915
Basic:
Weighted average shares (in shares)	111,424	113,187
Diluted:
Weighted average shares (in shares)	111,424	113,187
Dilutive effect of potential common shares (in shares)	1,072	671
Diluted weighted average shares (in shares)	112,496	113,858
Net income per share:
Basic (in usd per share)	$ 0.99	$ 0.79
Diluted (in usd per share)	$ 0.98	$ 0.79