Co-investments (Details) (USD $)	1 Months Ended	3 Months Ended		9 Months Ended																							9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		9 Months Ended		1 Months Ended			9 Months Ended				1 Months Ended		3 Months Ended			9 Months Ended
	Aug. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Membership interest in Wesco I [Member]	Dec. 31, 2012 Membership interest in Wesco I [Member]	Sep. 30, 2013 Membership interest in Wesco III [Member]	Dec. 31, 2012 Membership interest in Wesco III [Member]	Sep. 30, 2013 Partnership interest in Fund II [Member]	Dec. 31, 2012 Partnership interest in Fund II [Member]	Sep. 30, 2013 Membership interest in a limited liability company that owns Expo [Member]	Dec. 31, 2012 Membership interest in a limited liability company that owns Expo [Member]	Sep. 30, 2013 Total operating co-investments [Member]	Dec. 31, 2012 Total operating co-investments [Member]	Sep. 30, 2013 Membership interests in limited liability companies that own and are developing Epic, Connolly Station, Mosso I & II , and Elkhorn [Member]	Dec. 31, 2012 Membership interests in limited liability companies that own and are developing Epic, Connolly Station, Mosso I & II , and Elkhorn [Member]	Sep. 30, 2013 Membership interest in a limited liability company that owns and is developing Valley Village [Member]	Dec. 31, 2012 Membership interest in a limited liability company that owns and is developing Valley Village [Member]	Sep. 30, 2013 Membership interests in limited liability companies that own and are developing The Huxley and The Dylan [Member]	Dec. 31, 2012 Membership interests in limited liability companies that own and are developing The Huxley and The Dylan [Member]	Sep. 30, 2013 Membership interests in limited liability companies that owns and is developing One South Market [Member]	Dec. 31, 2012 Membership interests in limited liability companies that owns and is developing One South Market [Member]	Sep. 30, 2013 Total development co-investments [Member]	Dec. 31, 2012 Total development co-investments [Member]	Sep. 30, 2013 Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a preferred return of 10.1% [Member]	Dec. 31, 2012 Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a preferred return of 10.1% [Member]	Sep. 30, 2013 Preferred interests in related party limited liability companies that owns Sage at Cupertino with a preferred return of 9.5% [Member]	Dec. 31, 2012 Preferred interests in related party limited liability companies that owns Sage at Cupertino with a preferred return of 9.5% [Member]	Sep. 30, 2013 Preferred interest in a related party limited liability company that owns Madison Park at Anaheim with a preferred return of 9% [Member]	Dec. 31, 2012 Preferred interest in a related party limited liability company that owns Madison Park at Anaheim with a preferred return of 9% [Member]	Sep. 30, 2013 Preferred interest in related party limited liability company that owns an apartment development in Redwood City with a preferred return of 9.5% [Member]	Dec. 31, 2012 Preferred interest in related party limited liability company that owns an apartment development in Redwood City with a preferred return of 9.5% [Member]	Sep. 30, 2013 Preferred interest in a limited liability company that owns an apartment development in San Jose with a preferred return of 12% [Member]	Dec. 31, 2012 Preferred interest in a limited liability company that owns an apartment development in San Jose with a preferred return of 12% [Member]	Jun. 30, 2013 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member]	Sep. 30, 2013 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member]	Dec. 31, 2012 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member]	Sep. 30, 2013 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member] Minimum [Member]	Sep. 30, 2013 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% repaid in 2013 [Member] Maximum [Member]	Sep. 30, 2013 Total preferred interest investments [Member]	Dec. 31, 2012 Total preferred interest investments [Member]	Mar. 31, 2013 Preferred interest in limited liability company that owns an apartment community in downtown Los Angeles with a preferred return 10%	Jan. 31, 2013 Preferred equity Interest investment [Member]	Sep. 30, 2013 Preferred equity Interest investment [Member]	Sep. 30, 2013 Total co investment [Member]	Sep. 30, 2012 Total co investment [Member]	Sep. 30, 2013 Total co investment [Member]	Sep. 30, 2012 Total co investment [Member]	Dec. 31, 2012 Total co investment [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	$ 8,500,000	$ 674,075,000		$ 674,075,000		$ 571,345,000	$ 142,362,000	$ 143,874,000	$ 37,766,000	$ 9,941,000	$ 4,301,000	$ 53,601,000	$ 18,356,000	$ 18,752,000	$ 202,785,000	$ 226,168,000	$ 264,502,000	$ 186,362,000	$ 30,071,000	$ 0	$ 17,894,000	$ 16,552,000	$ 17,009,000	$ 0	$ 329,476,000	$ 202,914,000	$ 93,983,000	$ 91,843,000	$ 16,159,000	$ 14,438,000	$ 13,824,000	$ 13,175,000	$ 9,234,000	$ 0	$ 8,614,000	$ 0		$ 0	$ 22,807,000			$ 141,814,000	$ 142,263,000		$ 8,600,000
Preferred return rate (in hundredths)	12.00%																										10.10%		9.50%		9.00%		9.50%		12.00%					9.00%	10.00%				12.00%
Preferred equity redemption																																					13,100,000							9,700,000
Early redemption penalties																																					500,000							400,000
Investment period	3 years
Preferred equity investment, reduction rate, minimum (in hundredths)		9.00%
Preferred equity investment, reduction rate, maximum (in hundredths)		13.00%
Extended investment period		1 year
Income from preferred equity restructuring agreement		40,802,000	3,547,000	52,295,000	8,998,000																																									400,000
Balance sheets [Abstract]
Rental properties and real estate under development		45,804,000		45,804,000		66,851,000																																									1,676,935,000		1,676,935,000		1,745,147,000
Other assets																																															81,991,000		81,991,000		168,061,000
Total assets																																															1,758,926,000		1,758,926,000		1,913,208,000
Debt																																															659,112,000		659,112,000		820,895,000
Other liabilities		22,366,000		22,366,000		22,167,000																																									105,879,000		105,879,000		91,922,000
Equity																																															993,935,000		993,935,000		1,000,391,000
Total liabilities and equity																																															1,758,926,000		1,758,926,000		1,913,208,000
Company's share of equity																																															674,075,000		674,075,000		571,345,000
Statement of operations [Abstract]
Property revenues																																															24,796,000	34,425,000	78,913,000	96,981,000
Property operating expenses																																															(9,470,000)	(12,686,000)	(29,172,000)	(35,852,000)
Net property operating income																																															15,326,000	21,739,000	49,741,000	61,129,000
Gain on sale of real estate																																															137,845,000	0	146,663,000	0
Interest expense		(26,187,000)	(25,064,000)	(77,724,000)	(74,380,000)																																										(6,052,000)	(9,453,000)	(18,924,000)	(25,790,000)
General and administrative		(6,075,000)	(5,276,000)	(18,925,000)	(16,440,000)																																										(2,119,000)	(916,000)	(5,172,000)	(2,632,000)
Depreciation and Amortization		(3,005,000)	(2,927,000)	(8,937,000)	(8,681,000)																																										(8,718,000)	(12,821,000)	(29,314,000)	(35,593,000)
Net (loss) income																																															136,282,000	(1,451,000)	142,994,000	(2,886,000)
Company's share of net income																																															$ 40,802,000	$ 3,547,000	$ 52,295,000	$ 8,998,000