NET INCOME PER COMMON SHARE - Basic and Diluted Net Income Per Common Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Numerator for basic net income per common share: [Abstract]
Net income	$ 32,391	$ 24,702	$ 107,346	$ 89,514
Redemption premiums paid on Series A and Series B preferred shares	0	0	0	(19,924)
Preferred share dividends	(3,529)	(3,188)	(10,216)	(14,325)
Earnings participation of unvested stock awards	(24)	(32)	(58)	(96)
Numerator for basic net income per common share	28,838	21,482	97,072	55,169
Denominator for basic net income per common share: [Abstract]
Weighted average common shares outstanding (in shares)	95,793	95,761	95,779	95,647
Average unvested stock awards outstanding (in shares)	(388)	(493)	(395)	(508)
Denominator for basic net income per common share (in shares)	95,405	95,268	95,384	95,139
Basic net income per common share (in dollars per share)	$ 0.30	$ 0.23	$ 1.02	$ 0.58
Numerator for diluted net income per common share: [Abstract]
Net income available to common stockholders	28,838	21,482	97,072	55,169
Dividends on dilutive convertible preferred shares	0	0	0	44
Numerator for diluted net income per common share	$ 28,838	$ 21,482	$ 97,072	$ 55,213
Denominator for diluted net income per common share: [Abstract]
Basic weighted average common shares outstanding (in shares)	95,405	95,268	95,384	95,139
Net effect of dilutive equity awards	272	148	230	133
Net effect of dilutive convertible preferred shares (in shares)	0	0	0	101
Denominator for diluted net income per common share (in shares)	95,677	95,416	95,614	95,373
Diluted net income per common share (in dollars per share)	$ 0.30	$ 0.23	$ 1.02	$ 0.58