Reportable Segments - Summary of Revenues from Operating Properties, Loan Assets and REIT Securities and Expenses Incurred by Each Segment (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Segment Reporting Information [Line Items]
Net income from segments before corporate income (expense)	$ 872	$ 14,607
Rents and reimbursements	19,507	12,054
Interest and dividends	5,497	5,320
Gain (loss) on sale of securities carried at fair value	2	(102)
Real estate taxes	(2,194)	(737)
Equity in (loss) income of equity investments	6,194	7,869
Operating income	25,004	17,374
Depreciation and amortization expense	(7,399)	(4,154)
Interest expense	(5,693)	(5,691)
General and administrative	(1,642)	(844)
Impairment loss on investments in real estate	(9,200)
Related party fees	(2,375)	(2,266)
(Loss) income from continuing operations before non-controlling	(4,907)	9,733
Net loss attributable to non-controlling interest	1,443	795
Income from discontinued operations	4,105	3,218
Net income attributable to Winthrop Realty Trust	641	13,746
Discount accretion	1,205	716
Operating Segments [Member]
Segment Reporting Information [Line Items]
Rents and reimbursements	19,507	12,054
Operating expenses	(7,434)	(3,685)
Real estate taxes	(2,194)	(737)
Operating income	14,236	10,742
Depreciation and amortization expense	(7,399)	(4,154)
Interest expense	(3,771)	(3,284)
Impairment loss on investments in real estate	(9,200)
Operating properties net (loss) income	(6,134)	3,304
Operating Segments [Member] | Fenway-Wateridge [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	7	202
Equity in (loss) income of equity investments	52	36
Operating Segments [Member] | Sealy Northwest Atlanta [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(128)	(146)
Operating Segments [Member] | Marc Realty [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(5)	(60)
Operating Segments [Member] | WRT Elad [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	1,236	443
Operating Segments [Member] | Vintage Housing [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	1,620	1,921
Operating Segments [Member] | 701 Seventh [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	1,558	697
Operating Segments [Member] | Mentor [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	20	17
Operating Segments [Member] | Atrium Mall [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(3)
Loan Assets [Member]
Segment Reporting Information [Line Items]
Interest	4,292	4,454
Operating income	7,341	10,131
Interest expense	(121)	(580)
General and administrative	(216)	(14)
Operating properties net (loss) income	7,004	9,537
Discount accretion	1,205	716
Loan Assets [Member] | ROIC Lakeside Eagle [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(11)	(13)
Loan Assets [Member] | Concord Debt Holdings [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	266	35
Loan Assets [Member] | CDH CDO LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	433	150
Loan Assets [Member] | Concord Debt Holdings [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	90	14
Loan Assets [Member] | CDH CDO [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	833	480
Loan Assets [Member] | WRT-Stamford LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	229	221
Loan Assets [Member] | RE CDO Management LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	4	3,770
Loan Assets [Member] | 10 Metrotech [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments		304
REIT Securities [Member]
Segment Reporting Information [Line Items]
Interest and dividends		150
Gain (loss) on sale of securities carried at fair value		(102)
Unrealized gain on securities carried at fair value	2	1,718
Operating properties net (loss) income		1,766
Reconciliations to GAAP Net Income [Member]
Segment Reporting Information [Line Items]
Interest	85	69
Interest expense	(1,801)	(1,827)
General and administrative	(1,426)	(830)
Related party fees	(2,375)	(2,266)
Transaction costs	(250)	(6)
State and local taxes	(12)	(14)
(Loss) income from continuing operations before non-controlling	(4,907)	9,733
Net loss attributable to non-controlling interest	1,443	795
(Loss) income from continuing operations	(3,464)	10,528
Income from discontinued operations	$ 4,105	$ 3,218