EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income (Numerator)
Income available to common stockholders, basic (in dollars)	$ 53,232	$ 63,716	$ 41,839	$ 55,253	$ 48,533	$ 56,750	$ 73,915	$ 63,004	$ 214,040	$ 242,202	$ 194,745
Income available to common stockholders, diluted (in dollars)									$ 214,040	$ 242,202	$ 194,745
Shares (Denominator)
Basic (in shares)	64,833	64,562	64,262	64,009	63,835	64,010	63,471	62,964	64,418	63,574	62,437
Total average equivalent shares (in shares)	67,265	66,922	66,384	66,111	66,192	66,702	66,232	65,349	66,657	66,150	64,958
Per Share Amount
Net income per share, basic (in dollars per share)	$ 0.82	$ 0.99	$ 0.65	$ 0.86	$ 0.76	$ 0.89	$ 1.16	$ 1.00	$ 3.32	$ 3.81	$ 3.12
Net income per share, diluted (in dollars per share)	$ 0.79	$ 0.95	$ 0.63	$ 0.84	$ 0.73	$ 0.85	$ 1.12	$ 0.96	$ 3.21	$ 3.66	$ 3.00
Stock options
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)									1,800	2,344	2,440
Restricted stock units
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)									439	232	81