Summary of Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands	9 Months Ended
	Sep. 30, 2011	Nov. 04, 2010	Sep. 12, 2008
Foster Wheeler AG's outstanding shares authorized for repurchase under the initial repurchase program, value			$ 750,000
Foster Wheeler AG's outstanding shares authorized for repurchase under additional authorizations, value		335,000
Foster Wheeler AG's outstanding shares authorized for repurchase remaining at the balance sheet date, value	260,601
The current period impact of out-of period corrections related to the reduction of final estimated profit	7,800
Global E and C Group [Member]
The current period impact of out-of period corrections related to the reduction of final estimated profit	3,200
Global Power Group [Member]
The current period impact of out-of period corrections related to the reduction of final estimated profit	$ 4,600