Net Income per Share - Shares and EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Net income	$ 333,995	$ 266,447	$ 187,000
Dilutive effect of potential common stock equivalents - stock options (in shares)	122	207	132
Net earnings per share:
Earnings per share, basic (in shares)	$ 7.78	$ 6.15	$ 4.28
Earnings per share, diluted (in shares)	$ 7.76	$ 6.12	$ 4.27