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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Trusts Ownership Interest In Subsidiaries [Abstract]
Net income attributable to Winthrop Realty Trust	$ 8,374	$ 3,358	$ 22,120	$ 11,611
Increase (decrease) in Winthrop Realty Trust paid in capital adjustments from transaction with non-controlling interest	51	(5,487)	103	(5,695)
Changes from net income attributable to Winthrop Realty Trust and transfers (to) from non-controlling interest	$ 8,425	$ (2,129)	$ 22,223	$ 5,916