Fair Value Measurements (Details 1) (USD $)	6 Months Ended
	Jul. 31, 2011
Reconciliation of financial assets and liabilities and redeemable noncontrolling interest measured at fair value on a recurring basis using significant unobservable inputs
Beginning Balance	$ (337,312,000)
Total realized and unrealized gains (losses):
Included in earnings	3,333,000
Included in other comprehensive income	(19,072,000)
Included in additional paid-in capital	(1,986,000)
Ending Balance	(355,037,000)
Fair Value Measurements (Textuals)
Notional amount of TRS borrowing subject to fair value adjustments	260,982,000
Redeemable Noncontrolling Interest [Member]
Reconciliation of financial assets and liabilities and redeemable noncontrolling interest measured at fair value on a recurring basis using significant unobservable inputs
Beginning Balance	(226,829,000)
Total realized and unrealized gains (losses):
Included in earnings	1,879,000
Included in other comprehensive income	0
Included in additional paid-in capital	(1,986,000)
Ending Balance	(226,936,000)
Interest Rate Swaps [Member]
Reconciliation of financial assets and liabilities and redeemable noncontrolling interest measured at fair value on a recurring basis using significant unobservable inputs
Beginning Balance	(102,387,000)
Total realized and unrealized gains (losses):
Included in earnings	0
Included in other comprehensive income	(19,072,000)
Included in additional paid-in capital	0
Ending Balance	(121,459,000)
Net Total Return Swap [Member]
Reconciliation of financial assets and liabilities and redeemable noncontrolling interest measured at fair value on a recurring basis using significant unobservable inputs
Beginning Balance	(30,034,000)
Total realized and unrealized gains (losses):
Included in earnings	8,918,000
Included in other comprehensive income	0
Included in additional paid-in capital	0
Settlement	903,000
Ending Balance	(20,213,000)
Fair value adjustment to the borrowing subject to TRS [Member]
Reconciliation of financial assets and liabilities and redeemable noncontrolling interest measured at fair value on a recurring basis using significant unobservable inputs
Beginning Balance	21,938,000
Total realized and unrealized gains (losses):
Included in earnings	(7,464,000)
Included in other comprehensive income	0
Included in additional paid-in capital	0
Settlement	(903,000)
Ending Balance	13,571,000
Total Return Swap Related [Member]
Reconciliation of financial assets and liabilities and redeemable noncontrolling interest measured at fair value on a recurring basis using significant unobservable inputs
Beginning Balance	(8,096,000)
Total realized and unrealized gains (losses):
Included in earnings	1,454,000
Included in other comprehensive income	0
Included in additional paid-in capital	0
Ending Balance	$ (6,642,000)