Non-controlling Interests - Schedule of Changes in Trust's Ownership Interest in Subsidiaries (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Equity [Abstract]
Net income attributable to Winthrop Realty Trust	$ 8,962	$ 8,374	$ 9,602	$ 22,120
Increase (decrease) in Winthrop Realty Trust paid in capital adjustments from transaction with non-controlling interests	0	51	0	103
Changes from net income attributable to Winthrop Realty Trust and transfers (to) from non-controlling interest	$ 8,962	$ 8,425	$ 9,602	$ 22,223