Reportable Segments - Summary of Revenues from Operating Properties, Loan Assets and REIT Securities and Expenses Incurred by Each Segment (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting Information [Line Items]
Rents and reimbursements									$ 61,103,000	$ 44,213,000	$ 35,848,000
Net Income from segments before corporate income (expense)									80,563,000	39,970,000	24,454,000
Discount accretion									4,121,000	8,333,000	13,401,000
Interest and other income									375,000	699,000	1,175,000
Gain on sale of securities carried at fair value									742,000	41,000	123,000
Real estate taxes									(5,876,000)	(3,672,000)	(3,541,000)
Realized gain on sale of loan securities carried at fair value										614,000
Equity in (loss) income of equity investments									22,641,000	14,843,000	(12,712,000)
Operating income	23,227,000	18,255,000	19,040,000	19,036,000	17,552,000	15,204,000	16,753,000	15,827,000	79,558,000	65,336,000	61,306,000
Depreciation and amortization expense									20,443,000	15,119,000	10,692,000
General and administrative									(4,363,000)	(3,529,000)	(3,527,000)
Related Party Fees									(9,289,000)	(8,953,000)	(7,690,000)
Interest expense									(23,412,000)	(16,995,000)	(14,001,000)
Impairment loss on investments in real estate										(1,738,000)	(4,600,000)
Provision for loss on loans receivable									(348,000)	0	0
Federal, state and local taxes									(430,000)	(232,000)	(376,000)
(Loss) gain on extinguishment of debt										(121,000)	9,258,000
Income from continuing operations before non-controlling interest									16,821,000	24,502,000	11,398,000
Non-controlling interest									4,290,000	247,000	(814,000)
Gain on consolidation of property											818,000
Operating Segments [Member]
Segment Reporting Information [Line Items]
Rents and reimbursements									61,103,000	44,213,000	35,848,000
Operating expenses									(20,724,000)	(13,614,000)	(12,437,000)
Real estate taxes									(5,876,000)	(3,672,000)	(3,541,000)
Operating income									48,453,000	29,545,000	19,546,000
Depreciation and amortization expense									20,443,000	(15,119,000)	(10,692,000)
Interest expense									(14,204,000)	(12,348,000)	(11,057,000)
Impairment loss on investments in real estate										(1,738,000)	(4,600,000)
(Loss) gain on extinguishment of debt										(121,000)	6,439,000
Settlement (expense) income									(411,000)		5,868,000
Gain on consolidation of property											818,000
Operating properties net income (loss)									46,594,000	219,000	(14,736,000)
Operating Segments [Member] | Fenway-Wateridge [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment									613,000
Equity in (loss) income of equity investments									183,000
Operating Segments [Member] | Marc Realty [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									(284,000)	33,000	(775,000)
Impairment loss									(7,687,000)		(15,764,000)
Operating Segments [Member] | Sealy Northwest Atlanta [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									(469,000)	(388,000)	4,308,000
Operating Segments [Member] | Sealy Airpark Nashville [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments											(1,034,000)
Operating Segments [Member] | Sealy Newmarket [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments										(2,811,000)	(2,936,000)
Operating Segments [Member] | Vintage [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									9,174,000	4,603,000	113,000
Operating Segments [Member] | WRT Elad [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									1,315,000	903,000
Operating Segments [Member] | Mentor [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									84,000	46,000
Operating Segments [Member] | 701 Seventh Avenue [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									3,424,000
Operating Segments [Member] | Atrium Mall LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									(90,000)
Operating Segments [Member] | F-II Co Invest LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments										232,000
Operating Segments [Member] | Sealy Equity Investment [Member]
Segment Reporting Information [Line Items]
Impairment loss											(5,294,000)
Loan Assets [Member]
Segment Reporting Information [Line Items]
Interest income									14,334,000	11,736,000	11,073,000
Discount accretion									4,121,000	8,333,000	13,401,000
Realized gain on sale of loan securities carried at fair value										614,000
Unrealized gain on loan securities carried at fair value									215,000	447,000	2,738,000
Operating income									35,661,000	33,355,000	36,220,000
General and administrative									(46,000)	(121,000)	(75,000)
Interest expense									(1,898,000)	(1,494,000)	(850,000)
Provision for loss on loans receivable									(348,000)
Operating properties net income (loss)									33,369,000	31,740,000	35,295,000
Loan Assets [Member] | Marc Realty [Member]
Segment Reporting Information [Line Items]
Equity in earnings of preferred equity investment											338,000
Loan Assets [Member] | Lex-Win Concord [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments											258,000
Loan Assets [Member] | Concord Debt Holdings [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									3,072,000	422,000	3,216,000
Loan Assets [Member] | CDH CDO LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									1,033,000	1,715,000	480,000
Loan Assets [Member] | Concord Debt Holdings (1) [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									64,000	(456,000)
Loan Assets [Member] | CDH CDO (1) [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									4,926,000	(997,000)
Loan Assets [Member] | Sealy ROIC Riverside [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments										706,000	936,000
Loan Assets [Member] | ROIC Lakeside Eagle [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									(25,000)	(42,000)	664,000
Loan Assets [Member] | 46th Street Gotham [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments											621,000
Loan Assets [Member] | Sofitel [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments											2,177,000
Loan Assets [Member] | RE CDO Management LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									3,709,000	67,000	46,000
Loan Assets [Member] | Socal Office Portfolio Loan LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									(2,000)	9,706,000	272,000
Loan Assets [Member] | WRT-Stamford LLC [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									930,000	769,000
Loan Assets [Member] | 10 Metrotech [Member]
Segment Reporting Information [Line Items]
Equity in (loss) income of equity investments									3,284,000	335,000
REIT Securities [Member]
Segment Reporting Information [Line Items]
Dividends										1,054,000	984,000
Gain on sale of securities carried at fair value									742,000	41,000	123,000
Unrealized gain on loan securities carried at fair value									(142,000)	6,916,000	2,788,000
Operating properties net income (loss)									600,000	8,011,000	3,895,000
Reconciliations to GAAP Net Income [Member]
Segment Reporting Information [Line Items]
Interest and other income									375,000	699,000	1,175,000
General and administrative									(4,317,000)	(3,408,000)	(3,452,000)
Related Party Fees									(9,289,000)	(8,953,000)	(7,690,000)
Transaction costs									(1,885,000)	(421,000)	(519,000)
Interest expense									(7,310,000)	(3,153,000)	(2,094,000)
Federal, state and local taxes									(430,000)	(232,000)	(376,000)
Income from continuing operations before non-controlling interest									16,821,000	24,502,000	11,398,000
Non-controlling interest									4,290,000	247,000	(814,000)
Income from continuing operations attributable to Winthrop Realty Trust									21,111,000	24,749,000	10,584,000
Reconciliations to GAAP Net Income [Member] | Series B-1 [Member]
Segment Reporting Information [Line Items]
Gain on sale of securities carried at fair value											$ (100,000)