Acquisitions and Dispositions (Details) $ in Thousands	1 Months Ended								3 Months Ended					9 Months Ended		12 Months Ended
	Jul. 31, 2015 USD ($)	Jun. 30, 2015 USD ($) ft² tenant_space	Apr. 30, 2015 USD ($)	Oct. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	May. 31, 2014 USD ($)	Jan. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2011 USD ($)	Jun. 18, 2015 USD ($)	Apr. 30, 2014 USD ($)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price														$ 31,760		$ 18,615
Net Proceeds														16,545		17,886
Gain														16,260		937
Loss on impairment									$ 884		$ 497			3,665	$ 17,753
Note receivable from sale of mall									18,347					18,347		19,811
Gain on Extinguishment of Debt									0		18,282			256	$ 60,942
Madison Plaza
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price	$ 5,700
Net Proceeds	5,472
Gain	$ 2,769
Eastgate Crossing
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price		$ 21,060
Net Proceeds		6,118
Gain		13,491
Earn out proceeds		$ 1,740
Minimum number of tenant spaces to be leased required to receive earn out proceeds | tenant_space		2
Minimum square feet per tenant space leased required to receive earn out proceeds | ft²		5,800
Mortgage loan assumed at sale		$ 14,570
Madison Square
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price			$ 5,000
Net Proceeds			4,955
Gain			$ 0
Loss on impairment										$ 2,620
Pemberton Plaza
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price					$ 1,975
Net Proceeds					1,886
Gain					0
Loss on impairment											$ 497
Foothills Plaza Expansion
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price						$ 2,640
Net Proceeds						2,387
Gain						$ 937
Lakeshore Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Gross Sales Price							$ 14,000
Net Proceeds							13,613
Gain							0
Loss on impairment												$ 106	$ 5,100
Columbia Place
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Loss on impairment																		$ 50,683
Balance of Non-recourse Debt				$ 27,265
Gain on Extinguishment of Debt				$ 27,171
Noncash or Part Noncash Divestiture, Interest Expense																3,181
Chapel Hill Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Loss on impairment																12,050
Balance of Non-recourse Debt					68,563
Gain on Extinguishment of Debt					$ 18,296
Noncash or Part Noncash Divestiture, Interest Expense																1,514
Citadel Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Loss on impairment																	$ 20,453
Balance of Non-recourse Debt								$ 68,169
Gain on Extinguishment of Debt								$ 43,932
Notes Receivable
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Note receivable from sale of mall									10,488					10,488		10,488
Notes Receivable | Lakeshore Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Note receivable from sale of mall							10,000
Cash | Lakeshore Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Net Proceeds							$ 4,000
Fair Value, Inputs, Level 3 | Lakeshore Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Fair value of real estate investments																				$ 13,780
Columbia Place Chapel Hill and Citadel Mall
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Balance of Non-recourse Debt																163,997
Gain on Extinguishment of Debt																$ 89,399
Mayfaire Town Center and Community Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business combination, ownership percentage																			100.00%
Revenue from acquiree included in consolidated financial statements									4,314					4,731
Income from acquiree included in consolidated financial statements									$ 526					$ 713
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land																			$ 39,598
Buildings and improvements																			139,818
Tenant improvements																			3,331
Above-market leases																			393
In-place leases																			22,673
Total assets																			205,813
Below-market leases																			(13,825)
Net assets acquired																			191,988
Adjustments | Mayfaire Town Center and Community Center
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land																			(620)
Buildings and improvements																			1,368
Tenant improvements																			(51)
Above-market leases																			114
In-place leases																			(465)
Total assets																			346
Below-market leases																			(346)
Net assets acquired																			0
Previously Reported | Mayfaire Town Center and Community Center
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net [Abstract]
Land																			40,218
Buildings and improvements																			138,450
Tenant improvements																			3,382
Above-market leases																			279
In-place leases																			23,138
Total assets																			205,467
Below-market leases																			(13,479)
Net assets acquired																			$ 191,988