Investments in Real Estate Entities (Details 3) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets:
Real estate, net	$ 1,617,627	$ 1,905,005
Other assets	72,290	164,183
Total assets	1,689,917	2,069,188
Liabilities and partners' capital:
Mortgage notes payable and credit facility	980,128	1,251,067
Other liabilities	24,884	32,257
Partners' capital	684,905	785,864
Total liabilities and partners' capital	1,689,917	2,069,188
Combined summary of the operating results of the accounted for using the equity method
Rental and other income	198,939	212,994	172,076
Operating and other expenses	(80,301)	(86,434)	(73,955)
Gain on sale of real estate	333,221	96,152	106,195
Interest expense, net	(61,458)	(61,404)	(53,904)
Depreciation expense	(52,116)	(61,002)	(47,748)
Net income	338,285	100,306	102,664
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	148,766	(11,154)	20,914
Business acquisition transaction costs expensed	(7,681)	44,052	9,593
Land held for development	180,516	300,364
Fund I
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of real estate	3,317
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	475	10,924	7,041
Fund II
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of real estate	21,624	2,790
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	24,808	6,206	2,130
US Fund
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	342	(661)	0
ACJV
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	1,579	2,569	0
CVP I, LLC
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of real estate	50,478
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	113,127	5,783	5,394
Equity in income of unconsolidated entities relating to the Company's recognition of promoted interest	61,218	5,527	5,260
MVPI LLC
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	1,651	1,137	493
Equity in income of unconsolidated entities relating to the Company's recognition of promoted interest	930	516
Brandywine
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	828	661	0
Arna Valley View LP
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	2,406	0	0
Residual JV
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of real estate	8,510
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	3,547	(38,332)	0
Avalon Del Rey LLC
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of real estate			45
Costs in excess of equity in underlying net assets of the respective investments	3,880	5,439
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	0	181	4,000
Juanita Village
Summary of the Company's equity in income of unconsolidated entities
Equity in income (loss) of unconsolidated entities	3	378	1,856
Joint Venture
Summary of the Company's equity in income of unconsolidated entities
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage	70.00%
Variable Interest Entity, Ownership Interest by Noncontrolling Interest	30.00%
Land held for development	11,161
Avalon Mission Oaks
Summary of the Company's equity in income of unconsolidated entities
Number of apartment homes acquired	160
Purchase price	47,000
Prepaid Expenses and Other Assets
Summary of the Company's equity in income of unconsolidated entities
Due from Related Parties	5,354
Unconsolidated Properties [Member] | Fund I
Combined summary of the operating results of the accounted for using the equity method
Gain on sale of real estate	$ 944	$ 11,484	$ 7,971