Federal and State Income Taxes - Summary of GAAP Net Income Attributable to Trust to Taxable Income (Detail) (USD $) In Thousands, 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
Income Tax Disclosure [Abstract]
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
Book/Tax differences from depreciation and amortization expense									9,563	5,297	4,588
Book/Tax differences of accretion of discount									(4,121)	(8,333)	(13,401)
Book/Tax differences of unrealized gains									(73)	(6,923)	(2,788)
Book/Tax differences on gains/losses from capital transactions									(14,848)	(1,876)	(5,842)
Book/Tax differences on Preferred Shares											1,428
Book/Tax differences for impairment losses									2,904	3,260	7,600
Book/Tax differences on investments in unconsolidated joint ventures									(17,880)	4,131	31,634
Other book/tax differences, net									4,194	(8,781)	(766)
Book/Tax differences on dividend income										(452)	(371)
Book/Tax differences of market discount										14,065	13,250
Taxable income									$ 8,517	$ 25,019	$ 46,265