Quarterly Results of Operations - Company's Unaudited Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	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
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 23,227	$ 18,255	$ 19,040	$ 19,036	$ 17,552	$ 15,204	$ 16,753	$ 15,827	$ 79,558	$ 65,336	$ 61,306
Net income (loss) attributable to Winthrop Realty Trust	(5,070)	11,728	8,374	13,746	(2,088)	15,108	3,358	8,253	28,778	24,631	10,933
Net income (loss) applicable to Common Shares	$ (7,946)	$ 8,835	$ 5,490	$ 10,943	$ (4,875)	$ 12,322	$ 571	$ 7,328	$ 17,325	$ 15,346	$ 10,009
Per share
Net income (loss) applicable to Common Shares, basic	$ (0.22)	$ 0.27	$ 0.17	$ 0.33	$ (0.15)	$ 0.37	$ 0.02	$ 0.22	$ 0.28	$ 0.46	$ 0.31
Net income (loss) applicable to Common Shares, diluted	$ (0.22)	$ 0.27	$ 0.17	$ 0.33	$ (0.15)	$ 0.37	$ 0.02	$ 0.22	$ 0.28	$ 0.46	$ 0.31