Quarterly financial data (Details Textuals) (USD $) In Thousands, unless otherwise specified	3 Months Ended					12 Months Ended
	Jul. 31, 2011	Jan. 31, 2011	Jul. 31, 2010	Apr. 30, 2010	Jan. 31, 2010	Oct. 31, 2011	Oct. 31, 2009
Quarterly financial data (Textuals) [Abstract]
Net income tax benefits					$ 3,500
Additional tax charges				5,255
Tax benefits			10,700
Unrecognized tax benefits	2,027					2,027	964
Fee paid to withdraw from a multiemployer employee pension fund	3,136					3,120
Tax benefit from changes in tax law		$ 1,242