NET INCOME PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Numerator for basic net income per common share [Abstract]
Net income	$ 27,353	$ 33,957
Preferred stock dividends	(3,826)	(3,742)
Earnings participation of unvested equity awards	(44)	(34)
Numerator for basic net income per common share	$ 23,483	$ 30,181
Denominator for basic net income per common share [Abstract]
Average number of shares of common stock outstanding (in shares)	95,913	95,825
Average unvested stock awards outstanding (in shares)	(299)	(356)
Denominator for basic net income per common share (in shares)	95,614	95,469
Basic net income per common share (in dollars per share)	$ 0.25	$ 0.32
Numerator for diluted net income per common share [Abstract]
Numerator for basic net income per common share	$ 23,483	$ 30,181
Denominator for diluted net income per common share [Abstract]
Denominator for basic net income per common share (in shares)	95,614	95,469
Net effect of dilutive equity awards (in shares)	131	205
Denominator for diluted net income per common share (in shares)	95,745	95,674
Diluted net income per common share (in dollars per share)	$ 0.25	$ 0.32
Redeemable Preferred Stock [Member] | Cumulative Redeemable Preferred Stock, Series E [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred stock, dividend rate	7.50%		7.50%