Co-Investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	$ 477,967		$ 477,967		$ 383,412
Balance sheets: [Abstract]
Rental properties and real estate under development	60,020		60,020		44,280
Other Liabilities	20,886		20,886		20,528
Statement of operations: [Abstract]
Interest expense	(25,064)	(22,096)	(74,380)	(66,612)
General and administrative	(5,276)	(4,966)	(16,440)	(15,626)
Depreciation and Amortization	(2,927)	(2,936)	(8,681)	(8,527)
Membership interest in Wesco I [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	83,006		83,006		75,588
Partnership interest in Fund II [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	60,225		60,225		64,294
Membership interest in a limited liability company that owns Essex Skyline at MacArthur Place [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	0		0		24,063
Total operating co-investments [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	143,231		143,231		163,945
Membership interests in limited liability companies that own and are developing Epic, Lync, Elkhorn, and Folsom and Fifth [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	158,786		158,786		62,897
Membership interest in a limited liability company that owns and is developing Expo [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	18,759		18,759		17,981
Membership interests in limited liability companies that own and are developing Fountain at La Brea and Santa Monica at La Brea [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	16,189		16,189		15,194
Total development co-investments [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	193,734		193,734		96,072
Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a preferred return of 10.1% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	90,910		90,910		88,075
Preferred return rate (in hundredths)			10.10%
Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	22,807		22,807		22,792
Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% [Member] | Minimum [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Preferred return rate (in hundredths)			9.00%
Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% [Member] | Maximum [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Preferred return rate (in hundredths)			10.00%
Preferred interests in related party limited liability companies that owns Sage at Cupertino with a preferred return of 9.5% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	14,320		14,320
Preferred return rate (in hundredths)			9.50%
Preferred interest in a related limited liability company that owns Madison Park at Anaheim with a preferred return of 13% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	12,965		12,965		12,528
Preferred return rate (in hundredths)			13.00%
Total preferred interest investments [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	141,002		141,002		123,395
Total co investment [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	$ 477,967		$ 477,967		$ 383,412