Borrowings (Narrative) (Details) (US Senior Credit Agreement [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010
US Senior Credit Agreement [Member]
Line of Credit Facility, Description on U.S. Senior Secured Credit Agreement	U.S. Senior Secured Credit Agreement — On July 30, 2010, Foster Wheeler AG, Foster Wheeler Ltd., certain of Foster Wheeler Ltd.’s subsidiaries and BNP Paribas, as Administrative Agent, entered into a four-year amendment and restatement of our U.S. senior secured credit agreement, which we entered into in October 2006. The amended and restated U.S. senior secured credit agreement provides for a facility of $450,000, and includes a provision which permits future incremental increases of up to an aggregate of $225,000 in total additional availability under the facility. The amended and restated U.S. senior secured credit agreement permits us to issue up to $450,000 in letters of credit under the facility. Letters of credit issued under the amended and restated U.S. senior secured credit agreement have performance pricing that is decreased (or increased) as a result of improvements (or reductions) in our corporate credit rating as reported by Moody’s Investors Service, which we refer to as Moody’s, and/or Standard & Poor’s, or S&P. We received a corporate credit rating of BBB- as issued by S&P during the third quarter of 2010, which, under the amended and restated U.S. senior secured credit agreement, reduces our pricing for letters of credit issued under the agreement. Based on our current credit ratings, letter of credit fees for performance and financial letters of credit issued under the amended and restated U.S. senior secured credit agreement are 1.000% and 2.000% per annum of the outstanding amount, respectively, excluding fronting fees. We also have the option to use up to $100,000 of the $450,000 for revolving borrowings at a rate equal to adjusted LIBOR, as defined in the agreement, plus 2.000%, subject also to the performance pricing noted above.
Letters of credit capacity under the credit facility	$ 450,000
Fees and expenses in conjunction with the execution of senior credit agreement	4,300
Letters of credit facility, amount outstanding	$ 306,800	$ 310,100
Letter of credit fees under U.S. senior secured credit agreement, Minimum	1.00%	1.00%
Letter of credit fees under U.S. senior secured credit agreement, Maximum	2.00%	2.00%