Non-controlling Interests - Schedule of Changes in Trust's Ownership Interest in Subsidiaries (Detail) (USD $) In Thousands, unless otherwise specified	1 Months Ended	3 Months Ended	7 Months Ended	9 Months Ended
	Jul. 31, 2014	Sep. 30, 2013	Jul. 31, 2014	Sep. 30, 2013
Equity [Abstract]
Net income attributable to Winthrop Realty Trust	$ 2,879	$ 11,728	$ 12,481	$ 33,848
Increase (decrease) in Winthrop Realty Trust paid in capital adjustments from transaction with non-controlling interests				103
Changes from net income attributable to Winthrop Realty Trust and transfers (to) from non-controlling interest	$ 2,879	$ 11,728	$ 12,481	$ 33,951