Quarterly Results of Operations - Company's Unaudited Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 8,479	$ 22,917	$ 24,560	$ 55,956			$ 70,320
Net income (loss) attributable to Winthrop Realty Trust	2,879	8,962	641	12,481	$ 10,310	$ 12,481	28,778
Net income (loss) applicable to Common Shares	$ 1,939	$ 6,079	$ (2,242)	$ 5,787			$ 17,325
Per share
Net income (loss) applicable to Common Shares, basic	$ 0.05	$ 0.17	$ (0.06)	$ (0.15)			$ 0.25
Net income (loss) applicable to Common Shares, diluted	$ 0.05	$ 0.17	$ (0.06)	$ (0.15)			$ 0.25