EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Income (Numerator)
Income available to common stockholders (in dollars)	$ 59,048	$ 57,539	$ 102,911	$ 102,710
Shares (Denominator)
Basic (in shares)	63,053	62,697	62,888	62,496
Total average equivalent shares	64,785	64,276	65,063	64,603
Per Share Amount
Net income per share, basic (in dollars per share)	$ 0.94	$ 0.92	$ 1.64	$ 1.64
Net income per share, diluted (in dollars per share)	$ 0.91	$ 0.90	$ 1.58	$ 1.59
Stock options
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	1,693	1,550	2,128	2,075
Restricted stock units
Shares (Denominator)
Effect of dilutive stock based compensation (in shares)	39	29	47	32