Non-controlling Interests - Schedule of Changes in Trust's Ownership Interest in Subsidiaries (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Trusts Ownership Interest In Subsidiaries [Abstract]
Net income attributable to Winthrop Realty Trust	$ 11,728	$ 15,108	$ 33,848	$ 26,719
Increase (decrease) in Winthrop Realty Trust's paid in capital related to purchases of non-controlling interests			103	(5,695)
Changes from net income attributable to Winthrop Realty Trust and transfers (to) from non-controlling interests	$ 11,728	$ 15,108	$ 33,951	$ 21,024