NET INCOME PER COMMON SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Numerator for basic net income per common share [Abstract]
Net income	$ 16,440	$ 21,067	$ 65,423	$ 79,968
Preferred stock dividends	(3,846)	(3,809)	(11,515)	(11,339)
Earnings participation of unvested equity awards	(40)	(28)	(123)	(95)
Numerator for basic net income per common share	$ 12,554	$ 17,230	$ 53,785	$ 68,534
Denominator for basic net income per common share [Abstract]
Average number of shares of common stock outstanding (in shares)	95,978	95,814	95,946	95,814
Average unvested stock awards outstanding (in shares)	(300)	(284)	(299)	(314)
Denominator for basic net income per common share (in shares)	95,678	95,530	95,647	95,500
Basic net income per common share (in dollars per share)	$ 0.13	$ 0.18	$ 0.56	$ 0.72
Numerator for diluted net income per common share [Abstract]
Numerator for basic net income per common share	$ 12,554	$ 17,230	$ 53,785	$ 68,534
Denominator for diluted net income per common share [Abstract]
Denominator for basic net income per common share (in shares)	95,678	95,530	95,647	95,500
Net effect of dilutive equity awards (in shares)	188	191	152	195
Denominator for diluted net income per common share (in shares)	95,866	95,721	95,799	95,695
Diluted net income per common share (in dollars per share)	$ 0.13	$ 0.18	$ 0.56	$ 0.72
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%