SUMMARIZED CONDENSED CONSOLIDATING INFORMATION (Condensed Consolidating Balance Sheet) (Details) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Mar. 21, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets
Real estate investments, net of accumulated depreciation	$ 809,271		$ 827,135
Loans receivable and other investments, net	46,123		12,017
Cash and cash equivalents	96,641		17,101	30,477	42,250	42,250
Restricted cash	6,809		4,589
Deferred tax assets	24,212		24,212
Assets held for sale, net	0		2,215
Prepaid expenses, deferred financing costs and other assets	44,194		29,613
Due from Affiliates	0		0
Investments in subsidiaries	0		0
Total assets	1,027,250		916,882
Liabilities and stockholders’ equity
Mortgage notes payable	142,241		152,322
Secured revolving credit facility	0		92,500
Senior unsecured notes payable	414,538		330,666
Accounts payable and accrued liabilities	23,069		11,694
Tax liability	24,212		24,212
Intercompany	0		0
Total liabilities	604,060		611,394
Preferred Stock, Value, Issued	58		0
Stockholders’ equity
Common stock	373		371
Additional paid-in capital	494,802		353,861
Cumulative distributions in excess of net income	(72,043)		(48,744)
Total stockholders’ equity	423,190		305,488	311,319		326,573
Total liabilities and stockholders’ equity	1,027,250		916,882
Preferred stock, par value	$ 0.01		$ 0.01
Preferred stock, shares authorized	10,000,000		10,000,000
Preferred stock, shares issued	5,750,000	5,800,000	0
Preferred stock, shares outstanding	5,750,000		0
Common stock, par value	$ 0.01		$ 0.01
Common stock, shares authorized	125,000,000		125,000,000
Common stock, shares issued	37,333,943		37,099,209
Common stock, shares outstanding	37,333,943		37,099,209
Parent Company [Member]
Assets
Real estate investments, net of accumulated depreciation	113		151
Loans receivable and other investments, net	0		0
Cash and cash equivalents	95,887		15,075	27,791		41,736
Restricted cash	0		0
Deferred tax assets	24,212		24,212
Assets held for sale, net			0
Prepaid expenses, deferred financing costs and other assets	576		1,315
Due from Affiliates	0		0
Investments in subsidiaries	382,334		351,632
Total assets	503,122		392,385
Liabilities and stockholders’ equity
Mortgage notes payable	0		0
Secured revolving credit facility			0
Senior unsecured notes payable	0		0
Accounts payable and accrued liabilities	5,222		3,281
Tax liability	24,212		24,212
Intercompany	50,498		59,404
Total liabilities	79,932		86,897
Preferred Stock, Value, Issued	58		0
Stockholders’ equity
Common stock	373		371
Additional paid-in capital	494,802		353,861
Cumulative distributions in excess of net income	(72,043)		(48,744)
Total stockholders’ equity	423,190		305,488
Total liabilities and stockholders’ equity	503,122		392,385
Issuers [Member]
Assets
Real estate investments, net of accumulated depreciation	0		0
Loans receivable and other investments, net	0		0
Cash and cash equivalents	0		0	0		0
Restricted cash	0		0
Deferred tax assets	0		0
Assets held for sale, net			0
Prepaid expenses, deferred financing costs and other assets	9,402		7,339
Due from Affiliates	284,428		227,396
Investments in subsidiaries	514,017		451,975
Total assets	807,847		686,710
Liabilities and stockholders’ equity
Mortgage notes payable	0		0
Secured revolving credit facility			0
Senior unsecured notes payable	414,538		330,666
Accounts payable and accrued liabilities	10,975		4,412
Tax liability	0		0
Intercompany	0		0
Total liabilities	425,513		335,078
Preferred Stock, Value, Issued	0		0
Stockholders’ equity
Common stock	0		0
Additional paid-in capital	292,296		292,939
Cumulative distributions in excess of net income	90,038		58,693
Total stockholders’ equity	382,334		351,632
Total liabilities and stockholders’ equity	807,847		686,710
Combined Guarantor Subsidiaries [Member]
Assets
Real estate investments, net of accumulated depreciation	643,753		655,881
Loans receivable and other investments, net	46,123		12,017
Cash and cash equivalents	0		0	0		0
Restricted cash	1,040		92
Deferred tax assets	0		0
Assets held for sale, net			0
Prepaid expenses, deferred financing costs and other assets	29,136		18,133
Due from Affiliates	0		0
Investments in subsidiaries	24,930		23,142
Total assets	744,982		709,265
Liabilities and stockholders’ equity
Mortgage notes payable	0		0
Secured revolving credit facility			92,500
Senior unsecured notes payable	0		0
Accounts payable and accrued liabilities	6,060		3,348
Tax liability	0		0
Intercompany	273,637		205,458
Total liabilities	279,697		301,306
Preferred Stock, Value, Issued	0		0
Stockholders’ equity
Common stock	0		0
Additional paid-in capital	324,101		321,666
Cumulative distributions in excess of net income	141,184		86,293
Total stockholders’ equity	465,285		407,959
Total liabilities and stockholders’ equity	744,982		709,265
Combined Non-Guarantor Subsidiaries [Member]
Assets
Real estate investments, net of accumulated depreciation	165,405		171,103
Loans receivable and other investments, net	0		0
Cash and cash equivalents	754		2,026	2,686		514
Restricted cash	5,769		4,497
Deferred tax assets	0		0
Assets held for sale, net			2,215
Prepaid expenses, deferred financing costs and other assets	5,080		2,826
Due from Affiliates	39,707		37,466
Investments in subsidiaries	0		0
Total assets	216,715		220,133
Liabilities and stockholders’ equity
Mortgage notes payable	142,241		152,322
Secured revolving credit facility			0
Senior unsecured notes payable	0		0
Accounts payable and accrued liabilities	812		653
Tax liability	0		0
Intercompany	0		0
Total liabilities	143,053		152,975
Preferred Stock, Value, Issued	0		0
Stockholders’ equity
Common stock	0		0
Additional paid-in capital	49,772		53,952
Cumulative distributions in excess of net income	23,890		13,206
Total stockholders’ equity	73,662		67,158
Total liabilities and stockholders’ equity	216,715		220,133
Elimination [Member]
Assets
Real estate investments, net of accumulated depreciation	0		0
Loans receivable and other investments, net	0
Cash and cash equivalents	0		0	0		0
Restricted cash	0		0
Deferred tax assets	0		0
Assets held for sale, net			0
Prepaid expenses, deferred financing costs and other assets	0		0
Due from Affiliates	(324,135)		(264,862)
Investments in subsidiaries	(921,281)		(826,749)
Total assets	(1,245,416)		(1,091,611)
Liabilities and stockholders’ equity
Mortgage notes payable	0		0
Senior unsecured notes payable	0		0
Accounts payable and accrued liabilities	0		0
Tax liability	0		0
Intercompany	(324,135)		(264,862)
Total liabilities	(324,135)		(264,862)
Preferred Stock, Value, Issued	0		0
Stockholders’ equity
Common stock	0		0
Additional paid-in capital	(666,169)		(668,557)
Cumulative distributions in excess of net income	(255,112)		(158,192)
Total stockholders’ equity	(921,281)		(826,749)
Total liabilities and stockholders’ equity	$ (1,245,416)		$ (1,091,611)