SHAREHOLDERS' EQUITY (Details) (USD $)	12 Months Ended		0 Months Ended		12 Months Ended				0 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 16, 2013 Series A LLC Preferred Shares	Jan. 17, 2013 Series A LLC Preferred Shares	Dec. 31, 2013 Series A LLC Preferred Shares	Dec. 31, 2013 Restricted common shares	Dec. 31, 2012 Restricted common shares	Dec. 31, 2011 Restricted common shares	Feb. 14, 2013 Restricted common shares Manager	Dec. 31, 2013 Restricted common shares Manager	Dec. 31, 2012 Restricted common shares Manager	Dec. 31, 2011 Restricted common shares Manager	Dec. 31, 2013 Restricted common shares Directors	Dec. 31, 2012 Restricted common shares Directors	Dec. 31, 2011 Restricted common shares Directors	Dec. 31, 2013 Common share options	Dec. 31, 2013 Common share options Maximum
Stock-based compensation
Preferred shares, shares issued	14,950,000	0		14,950,000
Gross proceeds from issue of preferred shares (in dollars)				$ 373,800,000
Net proceeds from issuance of preferred stock (in dollars)	361,622,000			362,000,000
Preferred shares, dividend rate (as a percent)			7.375%	7.375%	7.375%
Exercise price of share options granted, minimum (as a percent)																100.00%
Termination period from date of grant																	10 years
Authorized shares available to satisfy awards as of the balance sheet date																8,839,625
Vesting period									3 years
Restricted common share transactions
Unvested shares at the beginning of the period						531,190	386,521	1,309,604		438,937	240,845	1,097,000	92,253	145,676	212,604
Issued (in shares)						331,297	301,860	291,411		292,009	258,303	240,845	39,288	43,557	50,566
Vested (in shares)						(192,659)	(157,191)	(1,189,903)		(146,312)	(60,211)	(1,097,000)	(46,347)	(96,980)	(92,903)
Cancelled (in shares)								(24,591)							(24,591)
Unvested shares at the end of the period						669,828	531,190	386,521		584,634	438,937	240,845	85,194	92,253	145,676
Value of unvested restricted common shares granted (in dollars per share)										$ 12.19	$ 10.56	$ 8.73	$ 10.69	$ 9.26	$ 7.91
Unrecognized compensation cost (in dollars)						$ 3,400,000	$ 2,900,000	$ 2,100,000