Earnings Per Share - Computation of Basic Earnings and Diluted Earnings Per Share Data (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Numerator for basic and diluted earnings per share:
Net income	$ 44,170	$ 39,284	$ 106,676	$ 140,726
Net income	$ 44,170	$ 39,284	$ 106,676	$ 140,726
Denominator:
Weighted-average basic common shares outstanding (in shares)	40,888	40,261	40,805	40,013
Assumed conversion of dilutive securities:
Stock awards (in shares)	1,398	1,345	1,391	1,480
Convertible senior notes (in shares)	0	0	0	0
Denominator for diluted earnings per share - Adjusted weighted-average shares (in shares)	42,286	41,606	42,196	41,493
Earnings per common share:
Basic (usd per share)	$ 1.08	$ 0.98	$ 2.61	$ 3.52
Diluted (usd per share)	$ 1.04	$ 0.94	$ 2.53	$ 3.39