Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
	Jul. 31, 2013	Jul. 31, 2012	Jul. 31, 2013 Segment, Discontinued Operations [Member]	Jul. 31, 2012 Segment, Discontinued Operations [Member]
Net loss	$ (40,568,000)	$ (14,111,000)
Depreciation and amortization	160,232,000	100,261,000	1,987,000	6,994,000
Amortization of mortgage procurement costs	5,326,000	6,063,000	50,000	492,000
Impairment of real estate	8,055,000	460,000	0	4,090,000
Impairment of unconsolidated entities	0	390,000
Write-offs of abandoned development projects	777,000	13,659,000
(Gain) loss on extinguishment of debt	(19,431,000)	719,000	40,000	0
Net loss on land held for divestiture activity	7,555,000	6,458,000
Net gain on disposition of partial interests in rental properties	(4,932,000)	0
Net gain on change in control of interests	(2,762,000)	(6,766,000)
Deferred income tax expense (benefit)	(10,651,000)	26,963,000	242,000	(4,070,000)
Equity in earnings	(13,341,000)	(20,438,000)
Net (gain) loss on land held for divestiture activity of unconsolidated entities	(681,000)	41,887,000
Stock-based compensation expense	6,135,000	5,208,000
Amortization and mark-to-market adjustments of derivative instruments	11,989,000	(5,262,000)
Non-cash interest expense related to Senior Notes	220,000	186,000
Cash distributions from operations of unconsolidated entities	29,580,000	30,119,000
Gain on disposition of rental properties	16,831,000	9,281,000	(43,103,000)	(8,879,000)
Cost of sales of land included in projects under construction and development and completed rental properties	6,222,000	2,875,000
Decrease (increase) in land held for development and sale	309,000	(1,811,000)
Decrease in land held for divestiture	26,000	33,479,000
(Increase) decrease in notes and accounts receivable	(5,782,000)	11,355,000
Decrease in other assets	5,096,000	2,235,000
Decrease in accounts payable, accrued expenses and other liabilities	(42,551,000)	(14,743,000)
Net cash provided by operating activities	60,039,000	217,813,000
Cash Flows from Investing Activities
Capital expenditures	(242,091,000)	(442,098,000)
Payment of lease procurement costs	(4,763,000)	(5,886,000)
Increase in other assets	(18,505,000)	(19,140,000)
(Increase) decrease in restricted cash and escrowed funds used for investing purposes	(11,029,000)	187,297,000
Proceeds from disposition of rental properties	81,841,000	8,896,000
Decrease (increase) in investments in and advances to unconsolidated entities	21,966,000	(11,992,000)
Net cash used in investing activities	(172,581,000)	(282,923,000)
Cash Flows from Financing Activities
Proceeds from nonrecourse mortgage debt and notes payable	89,054,000	461,579,000
Principal payments on nonrecourse mortgage debt and notes payable	(183,107,000)	(329,184,000)
Borrowings on bank revolving credit facility	225,950,000	75,000,000
Payments on bank revolving credit facility	(225,950,000)	(75,000,000)
Proceeds from issuance of Convertible Senior Notes due 2020, net of $8,750 of issuance costs	291,250,000	0
Make-whole premium and inducements related to exchange of Senior Notes due 2014 for Class A common stock	(5,490,000)	0
Transaction costs related to exchange of Senior Notes due 2014 for Class A common stock	(2,300,000)	0
Redemption of Senior Notes due 2015	(53,253,000)	0
Deferred financing costs	(6,996,000)	(7,471,000)
Increase in restricted cash and escrowed funds used for financing purposes	(75,525,000)	(8,208,000)
Purchase of treasury stock	(3,167,000)	(1,591,000)
Exercise of stock options	1,042,000	13,000
Redemption of Series A preferred stock	(5,063,000)	0
Proceeds from equity call hedge related to the issuance of Series A preferred stock	10,231,000	0
Dividends paid to preferred shareholders	(185,000)	(7,700,000)
Contributions from noncontrolling interests	42,149,000	240,000
Distributions to noncontrolling interests	(6,365,000)	(19,188,000)
Acquisitions of noncontrolling interests	(6,010,000)	0
Net cash provided by financing activities	86,265,000	88,490,000
Net (decrease) increase in cash and equivalents	(26,277,000)	23,380,000
Cash and equivalents at beginning of period	333,220,000	217,486,000
Cash and equivalents at end of period	306,943,000	240,866,000
Operating Activities
Increase in land held for development and sale	(4,255,000)	(1,916,000)
Decrease (increase) in land held for divestiture	1,661,000	(5,538,000)
(Increase) decrease in notes and accounts receivable	(3,777,000)	6,912,000
Increase in other assets	(29,068,000)	(2,435,000)
(Decrease) increase in accounts payable, accrued expenses and other liabilities	(30,234,000)	6,701,000
Total effect on operating activities	(65,673,000)	3,724,000
Investing Activities
Decrease (increase) in projects under construction and development	24,935,000	(14,174,000)
Increase in completed rental properties	(49,746,000)	(2,995,000)
Decrease in restricted cash and escrowed funds	0	3,624,000
(Increase) decrease in investments in and advances to affiliates	(5,937,000)	9,524,000
Total effect on investing activities	(30,748,000)	(4,021,000)
Financing Activities
Increase (decrease) in nonrecourse mortgage debt and notes payable	116,092,000	(2,561,000)
(Decrease) increase in senior and subordinated debt	(218,675,000)	118,951,000
Increase in restricted cash and escrowed funds	0	(116,792,000)
Increase in treasury stock	(12,868,000)	0
Decrease in preferred stock	(5,489,000)	0
Increase in Class A common stock	4,680,000	0
Increase (decrease) in additional paid-in capital	183,986,000	(5,610,000)
Increase in redeemable noncontrolling interest	4,085,000	7,266,000
Increase (decrease) in noncontrolling interest	24,610,000	(957,000)
Total effect on financing activities	$ 96,421,000	$ 297,000