EARNINGS PER SHARE - Reconciliation of Basic and Diluted Earnings Per Share Computations (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
Numerator for basic and diluted earnings per share:
Net income	$ 65,443	$ 67,075	$ 21,736	$ 54,910	$ 29,023	$ 11,572	$ 154,254	$ 95,505
Denominator:
Basic shares outstanding (in shares)	54,411			55,592			54,553	55,646
Dilutive effect of outstanding stock awards (in shares)	296			146			309	186
Dilutive shares outstanding (in shares)	54,707			55,738			54,862	55,832
Basic earnings per share (in dollars per share)	$ 1.20			$ 0.99			$ 2.83	$ 1.72
Diluted earnings per share (in dollars per share)	$ 1.20			$ 0.99			$ 2.81	$ 1.71