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		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Segment Reporting Information [Line Items]
Rents and reimbursements	$ 15,593	$ 11,841	$ 30,101	$ 23,042
Interest and dividends	4,308	5,778	9,628	11,296
Depreciation and amortization expense	(4,950)	(4,008)	(9,840)	(7,273)
Gain (loss) on sale of securities carried at fair value	0	15	(102)	41
Real estate taxes	(1,659)	(884)	(2,542)	(2,003)
Equity in (loss) income of equity investments	4,524	818	12,393	1,242
Interest income	115	90	185	191
Loan discount accretion	761	2,726	1,477	5,559
Interest expense	(6,708)	(3,448)	(12,740)	(7,172)
Settlement expense	(134)		(134)
General and administrative expense	(1,098)	(782)	(1,945)	(1,665)
Related party fees	(2,291)	(2,298)	(4,557)	(4,325)
Operating properties net income (loss)	12,758	7,557	24,735	13,221
Income from continuing operations before non-controlling interest	1,177	2,562	11,063	9,609
Non-controlling interest	(629)	(473)	(1,424)	(1,374)
Income from discontinued operations	6,568	323	9,633	628
Operating Segments [Member]
Segment Reporting Information [Line Items]
Rents and reimbursements	15,593	11,841	30,101	23,042
Depreciation and amortization expense	(4,950)	(4,008)	(9,840)	(7,273)
Operating expenses	(4,892)	(3,355)	(9,650)	(7,530)
Real estate taxes	(1,659)	(884)	(2,542)	(2,003)
Equity in (loss) income of equity investments		232		232
Interest expense	(4,234)	(3,034)	(7,859)	(6,132)
Operating properties net income (loss)	3,440	515	6,902	(184)
Operating Segments [Member] | Fenway-Wateridge [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment	185		387
Equity in (loss) income of equity investments	47		83
Operating Segments [Member] | Sealy Northwest Atlanta [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(87)	(108)	(233)	(164)
Operating Segments [Member] | Sealy Newmarket [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments		(745)		(1,467)
Operating Segments [Member] | Marc Realty [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	69	3	9	(344)
Operating Segments [Member] | WRT Elad [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	167	(28)	610	515
Operating Segments [Member] | Vintage [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	2,696	595	4,617	934
Operating Segments [Member] | 701 Seventh Avenue [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	623		1,320
Operating Segments [Member] | Mentor [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	16	6	33	6
Loan Assets [Member]
Segment Reporting Information [Line Items]
Interest income	3,447	2,746	7,901	5,145
Loan discount accretion	761	2,726	1,477	5,559
Interest expense	(647)	(334)	(1,227)	(668)
Unrealized (loss) gain on securities carried at fair value	215	(88)	215	76
General and administrative expense	(21)	(20)	(35)	(25)
Operating properties net income (loss)	4,748	5,893	14,285	11,617
Loan Assets [Member] | Sealy ROIC Riverside [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments		234		468
Loan Assets [Member] | ROIC Lakeside Eagle [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(2)	(4)	(15)	(16)
Loan Assets [Member] | Concord Debt Holdings [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	36	55	71	351
Loan Assets [Member] | CDH CDO LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments		140	150	534
Loan Assets [Member] | Concord Debt Holdings (1) [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment	15	28	29	28
Loan Assets [Member] | CDH CDO (1) [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment	427	478	907	478
Loan Assets [Member] | WRT-Stamford [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	224	227	445	316
Loan Assets [Member] | SoCal Office Portfolio Loan [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(2)	(293)	(2)	(638)
Loan Assets [Member] | RE CDO Management LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	(9)	17	3,761	28
Loan Assets [Member] | 10 Metrotech [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments	304	(19)	608	(19)
REIT Securities [Member]
Segment Reporting Information [Line Items]
Interest and dividends	100	306	250	592
Gain (loss) on sale of securities carried at fair value		15	(102)	41
Unrealized (loss) gain on securities carried at fair value	(1,860)	(791)	(142)	4,141
Operating properties net income (loss)	(1,760)	(470)	6	4,774
Net Income Attributable to Winthrop Realty Trust	6,428	5,938	21,193	16,207
Reconciliations to GAAP Net Income [Member]
Segment Reporting Information [Line Items]
Interest income	115	90	185	191
Interest expense	(1,827)	(80)	(3,654)	(372)
General and administrative expense	(1,077)	(762)	(1,910)	(1,640)
Related party fees	(2,291)	(2,298)	(4,557)	(4,325)
Transaction costs	(46)	(184)	(52)	(305)
State and local taxes	(125)	(142)	(142)	(147)
Income from continuing operations before non-controlling interest	1,177	2,562	11,063	9,609
Non-controlling interest	629	473	1,424	1,374
Income from continuing operations	1,806	3,035	12,487	10,983
Income from discontinued operations	6,568	323	9,633	628
Net Income Attributable to Winthrop Realty Trust	$ 8,374	$ 3,358	$ 22,120	$ 11,611