NET INCOME PER SHARE Calculation of Basic and Diluted Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Basic net income per share:
Net income applicable to common stockholders	$ 14,780	$ 21,272
Weighted average common shares outstanding (in shares)	55,268	57,793
Basic net income per share (in usd per share)	$ 0.27	$ 0.37
Diluted net income per share:
Net income applicable to common stockholders	$ 14,780	$ 21,272
Dilutive shares from assumed conversion of convertible senior notes (in shares)	0	1,789
Dilutive stock options and restricted stock (in shares)	502	1,268
Diluted weighted average common shares outstanding (in shares)	55,770	60,850
Diluted net income per share (in usd per share)	$ 0.27	$ 0.35