Net Income per Share - Shares and EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Reconciliation of basic earnings per share ("EPS") to diluted EPS
Net income	$ 266,447	$ 187,000	$ 133,982
Basic weighted-average shares outstanding	43,325	43,709	44,735
Dilutive effect of potential common stock equivalents - stock options (in shares)	207	132	186
Diluted weighted-average shares outstanding	43,532	43,841	44,921
Net earnings per share:
Earnings Per Share, Basic	$ 6.15	$ 4.28	$ 3.00
Earnings Per Share, Diluted	$ 6.12	$ 4.27	$ 2.98