Reportable Segments - Summary of Revenues from Operating Properties, Loan Assets and REIT Securities and Expenses Incurred by Each Segment (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		7 Months Ended	12 Months Ended
	Jul. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Jul. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Rents and reimbursements				$ 46,313			$ 51,865
Gain on sale of securities carried at fair value				2			742
Interest and other income				244			375
Operating expenses				(17,127)			(17,769)
Discount accretion				2,086		$ 2,086	4,121
Unrealized gain (loss) on securities carried at fair value							(142)
Real estate taxes				(5,379)			(4,926)
Unrealized gain on loan securities carried at fair value							215
Equity in (loss) income of equity investments				12,622			22,641
Operating income	$ 8,479	$ 22,917	$ 24,560	55,956			70,320
Depreciation and amortization expense				(15,957)			(17,275)
General and administrative				(4,283)			(4,356)
Related party fees				(5,548)			(9,289)
Transaction costs				(586)			(1,885)
Interest expense				(13,394)			(22,365)
Loss on extinguishment of debt				(564)
Impairment loss on investments in real estate				(9,200)
Provision for loss on loans receivable				0			(348)
Federal, state and local taxes				60			(424)
Impairment loss on equity investments				2,422			7,687
Income (loss) from continuing operations				(2,572)			15,716
Settlement expense							(411)
Income from discontinued operations attributable to Winthrop Realty Trust				11,235			8,772
Non-controlling interest				3,818			4,290
Net income attributable to Winthrop Realty Trust	$ 2,879	$ 8,962	$ 641	12,481	$ 10,310	12,481	28,778
RE CDO Management LLC [Member]
Segment Reporting Information [Line Items]
Operating income					113	149	226
General and administrative					$ (58)	$ (79)	(290)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Net Income from segments before corporate income (expense)				11,832			38,561
Operating Segments [Member] | Operating Properties [Member]
Segment Reporting Information [Line Items]
Rents and reimbursements				46,313			51,865
Operating expenses				(17,127)			(17,769)
Real estate taxes				(5,379)			(4,926)
Operating income				35,880			43,120
Depreciation and amortization expense				(15,957)			(17,275)
Interest expense				(9,323)			(13,157)
Impairment loss on investments in real estate				(9,200)
Settlement expense							(411)
Operating properties net income (loss)				(1,022)			4,590
Operating Segments [Member] | Operating Properties [Member] | Fenway-Wateridge [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment				17			613
Equity in (loss) income of equity investments				142			183
Operating Segments [Member] | Operating Properties [Member] | Vintage Housing Holdings [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment				565
Equity in (loss) income of equity investments				4,287			9,174
Operating Segments [Member] | Operating Properties [Member] | Marc Realty [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				(19)			(284)
Impairment loss on equity investments				(2,422)			(7,687)
Operating Segments [Member] | Operating Properties [Member] | Sealy Northwest Atlanta [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				(288)			(469)
Operating Segments [Member] | Operating Properties [Member] | WRT-Elad [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				2,927			1,315
Operating Segments [Member] | Operating Properties [Member] | Mentor Retail [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				43			84
Operating Segments [Member] | Operating Properties [Member] | 701 Seventh Avenue [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				4,393			3,424
Operating Segments [Member] | Operating Properties [Member] | Atrium Mall [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				7			(90)
Operating Segments [Member] | Operating Properties [Member] | Edens Properties [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				(1)
Operating Segments [Member] | Loan Assets [Member]
Segment Reporting Information [Line Items]
Interest income				7,557			14,334
Discount accretion				2,086			4,121
Unrealized gain on loan securities carried at fair value							215
Operating income				13,196			35,661
General and administrative				(223)			(44)
Interest expense				(121)			(1,898)
Provision for loss on loans receivable							(348)
Operating properties net income (loss)				12,852			33,371
Operating Segments [Member] | Loan Assets [Member] | Concord Debt Holdings [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				547			3,072
Operating Segments [Member] | Loan Assets [Member] | CDH CDO LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				1,065			1,033
Operating Segments [Member] | Loan Assets [Member] | Concord Debt Holdings from Lexington Realty Trust [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				87			64
Operating Segments [Member] | Loan Assets [Member] | CDH CDO [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				1,326			4,926
Operating Segments [Member] | Loan Assets [Member] | ROIC Lakeside Eagle [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				(20)			(25)
Operating Segments [Member] | Loan Assets [Member] | RE CDO Management LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				7			3,709
Operating Segments [Member] | Loan Assets [Member] | SoCal Office Loan Portfolio [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments							(2)
Operating Segments [Member] | Loan Assets [Member] | WRT-Stamford LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments				541			930
Operating Segments [Member] | Loan Assets [Member] | 10 Metrotech [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments							3,284
Operating Segments [Member] | REIT Securities [Member]
Segment Reporting Information [Line Items]
Gain on sale of securities carried at fair value				2			742
Unrealized gain (loss) on securities carried at fair value							(142)
Operating properties net income (loss)				2			600
Reconciliations to GAAP Net Income [Member]
Segment Reporting Information [Line Items]
Interest and other income				244			375
General and administrative				(4,060)			(4,312)
Related party fees				(5,548)			(9,289)
Transaction costs				(586)			(1,885)
Interest expense				(3,950)			(7,310)
Loss on extinguishment of debt				(564)
Federal, state and local taxes				$ 60			$ (424)