Acquisition and Disposition Activity - Additional Information (Detail) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended				0 Months Ended	6 Months Ended		6 Months Ended	0 Months Ended				0 Months Ended	6 Months Ended				0 Months Ended		3 Months Ended	0 Months Ended			4 Months Ended			6 Months Ended		6 Months Ended		0 Months Ended
	Feb. 07, 2014	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Investment	Jun. 30, 2013	Feb. 07, 2014	Dec. 31, 2013	Mar. 05, 2014 Edens Center and Norridge Commons [Member]	Jun. 30, 2014 Edens Center and Norridge Commons [Member]	Mar. 05, 2014 Edens Center and Norridge Commons [Member]	Jun. 30, 2014 EDITION Hotel [Member] sqft Room	Jan. 10, 2014 Playa Vista Mezzanine Loan [Member]	Jan. 10, 2014 Playa Vista Mezzanine Loan [Member]	Feb. 07, 2014 Legacy Orchard Loan [Member]	Feb. 07, 2014 Hotel Wales Loan [Member]	Mar. 05, 2014 Marc Realty [Member]	Jun. 30, 2014 Marc Realty [Member]	Mar. 05, 2014 Marc Realty [Member]	Jun. 30, 2014 Marc Realty [Member] Minimum [Member]	Jun. 30, 2014 Marc Realty [Member] Maximum [Member]	Mar. 05, 2014 Marc Realty [Member] First Anniversary [Member]	Mar. 05, 2014 Marc Realty [Member] Second Anniversary [Member]	Mar. 31, 2014 Queensridge [Member]	May 01, 2014 Crossroads I & II Property [Member]	Jun. 25, 2014 Amherst Property [Member]	Mar. 05, 2014 Norridge [Member]	Jun. 30, 2014 Norridge [Member]	Mar. 05, 2014 Norridge [Member]	Mar. 05, 2014 Edens Plaza Associates [Member]	Jun. 30, 2014 701 Seventh Avenue [Member] Agreement Room	Jan. 31, 2014 701 Seventh Avenue [Member] sqft	Jun. 30, 2014 701 Seventh Avenue [Member] Mortgage Loan [Member]	Jun. 30, 2014 701 Seventh Avenue [Member] Mezzanine Loan [Member]	Feb. 26, 2014 Newbury Apartments Property [Member]
Business Acquisition [Line Items]
Acquisition of issued and outstanding equities																												$ 250,000	$ 250,000
Percentage of ownership interest																										0.375%
Non-controlling interest recorded				16,391,000																						16,391,000
Net loss attributable to Winthrop Realty Trust		8,962,000	8,374,000	9,602,000	22,120,000																						(2,000)
Revenue		22,917,000	16,679,000	47,477,000	33,396,000																						2,061,000
Additional capital contributions																														43,825,000
Capital contributions																														96,722,000
Mortgage loan																															237,500,000
Mezzanine loan																															315,000,000
Area of collateralized building																															110,000
Land description																														Mezzanine loan to be advanced for construction costs of the approximately 110,000 square feet of retail space and an approximately 120 foot high, 20,000 square foot state of the art LED sign.
Loan bears interest, description of variable rate basis				LIBOR plus 3%																										LIBOR plus 8%
LIBOR plus																														8.00%
Maturity date of loan																														Jan. 31, 2017
Number of Automatic Extensions for building lease																														2
Extensions period for lease																																2 years	1 year
Supplemental loans amount																														262,500,000
Number rooms in hotel											452																			452
Maximum aggregate debt																														815,000,000
Office building area, square foot											30,000
Proceeds from sale of interest in real estate property				56,423,000	31,312,000																				24,500,000									27,500,000
Net proceeds																								29,633,000	21,226,000									5,106,000
Gain or loss on sale of property																								5,723,000	846,000									4,422,000
Gross proceeds from sale																6,000,000								31,100,000
Gross proceeds from sale, cash received																1,500,000
Gross proceeds from sale, note receivable		2,217,000		2,217,000			2,229,000											4,500,000
Interest rate, loan bears												16.25%				6.00%					7.00%	8.00%
Note interest maturity, date				Aug. 15, 2022													Mar. 01, 2017
Gain on sale of interest				3,000
Gain on sale of equity investments				69,000
Number of equity investments				3
Aggregate purchase price																			5,800,000	6,600,000
Revenue from reserve holdback																									2,483,000
Net proceeds from sale of real estate property																									23,709,000
Mortgage loan on real estate, increase in principal balance												4,000,000
Mortgage loan on real estate, increase in interest rate												1.50%
Mortgage loan on real estate, share in increased loan amount													2,000,000
Share funded amount												1,992,000
Loan secured by limited partnership interests, face amount										15,500,000
Loan secured by limited partnership interests, basis spread on variable rate								12.00%
Loan secured by limited partnership interests, increase in basis spread on variable rate in each extended term								1.00%
Loan secured by limited partnership interests, stated current interest rate								10.00%
Loan secured by limited partnership interests, annual increase in stated current interest rate								0.50%
Loan secured by limited partnership interests, term									3 years
Description of trusts participation interest in loan									Upon satisfaction of the loan, the Trust will be entitled to a participation interest equal to the greater of (i) a 14.5% internal rate of return ("IRR") (increasing to 15.5% IRR after the initial term) and (ii) 30% (increasing to 40% after the initial term and 50% after the first extended term) of the value of the properties in excess of $115,000,000.
Loan participation interest IRR percentage										14.50%
Loan participation interest IRR percentage after initial term										15.50%
Loan participation interest percentage										30.00%
Loan participation interest percentage after initial term										40.00%
Loan participation interest percentage after extended term										50.00%
Minimum value of properties for entitlement to loan participation interest										115,000,000
Sales of interest						42,900,000
Sale price net amount						29,150,000
Retained interest														2.50%	0.50%
Gain (loss) on sale of loan	0
Aggregate principle payments																							2,908,000
Trust received, exit fee																							$ 1,787,000