Gain Loss on Extinguishment of Debt (Details Textuals) (USD $)	3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013	Jul. 31, 2012
Extinguishment of Debt [Line Items]
Gain (loss) on extinguishment of debt	$ 24,669,000	$ 0	$ 19,431,000	$ (719,000)
Ten MetroTech Center [Member]
Extinguishment of Debt [Line Items]
Gain (loss) on extinguishment of debt			24,669,000
2014 Senior Notes [Member]
Extinguishment of Debt [Line Items]
Gain (loss) on extinguishment of debt			$ (4,762,000)