Commitments and Contingent Liabilities (Details Textual) (USD $)	Jun. 01, 2013
Long-term Purchase Commitment [Line Items]
Company's backlog bonded by performance bonds	$ 117,100,000
Face value of performance bonds	313,300,000
Total value of letter of credit	25,500,000
Line of Credit Facility, Maximum Borrowing Capacity	100,000,000
Purchase obligations	113,600,000
Other Commitment	100,000
Derivative, Notional Amount	24,300,000
Derivative Liability, Fair Value, Net	$ 500,000