NET INCOME PER COMMON SHARE - Components of Computation of Basic and Diluted Net Income Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Numerator for basic net income per common share [Abstract]
Net income	$ 21,067	$ 32,391	$ 79,968	$ 107,346
Preferred stock dividends	(3,809)	(3,529)	(11,339)	(10,216)
Earnings participation of unvested equity awards	(28)	(24)	(95)	(58)
Numerator for basic net income per common share	$ 17,230	$ 28,838	$ 68,534	$ 97,072
Denominator for basic net income per common share [Abstract]
Weighted average common stock outstanding (in shares)	95,814	95,793	95,814	95,779
Average unvested stock awards outstanding (in shares)	(284)	(388)	(314)	(395)
Denominator for basic net income per common share (in shares)	95,530	95,405	95,500	95,384
Basic net income per common share (in dollars per share)	$ 0.18	$ 0.30	$ 0.72	$ 1.02
Numerator for diluted net income per common share [Abstract]
Numerator for basic net income per common share	$ 17,230	$ 28,838	$ 68,534	$ 97,072
Denominator for diluted net income per common share [Abstract]
Denominator for basic net income per common share (in shares)	95,530	95,405	95,500	95,384
Net effect of dilutive equity awards (in shares)	191	272	195	230
Denominator for diluted net income per common share (in shares)	95,721	95,677	95,695	95,614
Diluted net income per common share (in dollars per share)	$ 0.18	$ 0.30	$ 0.72	$ 1.02