Fair Value Measurements (Details) (Fair value measurement, recurring basis [Member], USD $) In Thousands, unless otherwise specified	Apr. 30, 2012	Jan. 31, 2012
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Fair value adjustment to the borrowings subject to TRS	$ 9,325	$ 9,180
Redeemable noncontrolling interest	(230,438)	(229,149)
Fair value of financial assets and liabilities and redeemable noncontrolling interests on a recurring basis	(372,202)	(382,585)
Interest rate caps [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets	17	13
Interest rate swap agreements [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets	894	1,083
Derivative Liabilities	(141,145)	(148,699)
Total Return Swap [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets	13,500	10,308
Derivative Liabilities	(24,355)	(25,321)
Fair Value, Inputs, Level 1 [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Fair value adjustment to the borrowings subject to TRS
Redeemable noncontrolling interest
Fair value of financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Fair Value, Inputs, Level 1 [Member] | Interest rate caps [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets
Fair Value, Inputs, Level 1 [Member] | Interest rate swap agreements [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets
Derivative Liabilities
Fair Value, Inputs, Level 1 [Member] | Total Return Swap [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets
Derivative Liabilities
Fair Value, Inputs, Level 2 [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Fair value of financial assets and liabilities and redeemable noncontrolling interests on a recurring basis	(3,717)	(4,300)
Fair Value, Inputs, Level 2 [Member] | Interest rate caps [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets	17	13
Fair Value, Inputs, Level 2 [Member] | Interest rate swap agreements [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets	894	1,083
Derivative Liabilities	(4,628)	(5,396)
Fair Value, Inputs, Level 3 [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Fair value adjustment to the borrowings subject to TRS	9,325	9,180
Redeemable noncontrolling interest	(230,438)	(229,149)
Fair value of financial assets and liabilities and redeemable noncontrolling interests on a recurring basis	(368,485)	(378,285)
Fair Value, Inputs, Level 3 [Member] | Interest rate swap agreements [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Liabilities	(136,517)	(143,303)
Fair Value, Inputs, Level 3 [Member] | Total Return Swap [Member]
Company's financial assets and liabilities and redeemable noncontrolling interests on a recurring basis
Derivative Assets	13,500	10,308
Derivative Liabilities	$ (24,355)	$ (25,321)