Co-Investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended																			6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended			3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Jun. 30, 2012 Membership interest in Wesco I [Member]	Dec. 31, 2011 Membership interest in Wesco I [Member]	Jun. 30, 2012 Partnership interest in Fund II [Member]	Dec. 31, 2011 Partnership interest in Fund II [Member]	Jun. 30, 2012 Membership interest in a limited liability company that owns Essex Skyline at MacArthur Place [Member]	Dec. 31, 2011 Membership interest in a limited liability company that owns Essex Skyline at MacArthur Place [Member]	Jun. 30, 2012 Total operating co-investments [Member]	Dec. 31, 2011 Total operating co-investments [Member]	Jun. 30, 2012 Membership interests in limited liability companies that own and are developing Epic, Lync, Elkhorn, and Folsom and Fifth [Member]	Dec. 31, 2011 Membership interests in limited liability companies that own and are developing Epic, Lync, Elkhorn, and Folsom and Fifth [Member]	Jun. 30, 2012 Membership interest in a limited liability company that owns and is developing Expo [Member]	Dec. 31, 2011 Membership interest in a limited liability company that owns and is developing Expo [Member]	Jun. 30, 2012 Membership interests in limited liability companies that own and are developing Fountain at La Brea and Santa Monica at La Brea [Member]	Dec. 31, 2011 Membership interests in limited liability companies that own and are developing Fountain at La Brea and Santa Monica at La Brea [Member]	Jun. 30, 2012 Total development co-investments [Member]	Dec. 31, 2011 Total development co-investments [Member]	Jun. 30, 2012 Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a perferred return of 10.1% [Member]	Dec. 31, 2011 Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a perferred return of 10.1% [Member]	Jun. 30, 2012 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% [Member]	Dec. 31, 2011 Preferred interests in limited liability companies that own apartment communities in downtown Los Angeles with preferred returns of 9% and 10% [Member]	Jun. 30, 2012 Preferred interest in a related limited liability company that owns Madison Park at Anaheim with a preferred return of 13% [Member]	Dec. 31, 2011 Preferred interest in a related limited liability company that owns Madison Park at Anaheim with a preferred return of 13% [Member]	Jun. 30, 2012 Total preferred interest investments [Member]	Dec. 31, 2011 Total preferred interest investments [Member]	Jun. 30, 2012 Total co investment [Member]	Jun. 30, 2011 Total co investment [Member]	Jun. 30, 2012 Total co investment [Member]	Jun. 30, 2011 Total co investment [Member]	Dec. 31, 2011 Total co investment [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	$ 436,230		$ 436,230		$ 383,412	$ 83,919	$ 75,588	$ 61,560	$ 64,294	$ 0	$ 24,063	$ 145,479	$ 163,945	$ 130,870	$ 62,897	$ 18,518	$ 17,981	$ 15,830	$ 15,194	$ 165,218	$ 96,072	$ 89,986	$ 88,075	$ 22,792	$ 22,792	$ 12,755	$ 12,528	$ 125,533	$ 123,395	$ 436,230		$ 436,230		$ 383,412
Preferred return rate (in hundredths)			9.50%																			10.10%	10.10%	9.00%	10.00%	13.00%	13.00%
Balance sheets: [Abstract]
Rental properties and real estate under development	55,343		55,343		44,280																									1,625,272		1,625,272		1,659,078
Other Assets																														77,879		77,879		63,847
Total assets																														1,703,151		1,703,151		1,722,925
Debt																														838,003		838,003		900,095
Other Liabilities	20,724		20,724		20,528																									59,915		59,915		48,518
Equity																														805,233		805,233		774,312
Total liabilities and equity																														1,703,151		1,703,151		1,722,925
Company's share of equity																														436,230		436,230		383,412
Statement of operations: [Abstract]
Property revenues																														28,233	24,084	62,556	42,596
Property operating expenses																														(10,029)	(9,719)	(23,166)	(17,695)
Net property operating income																														18,204	14,365	39,390	24,901
Interest expense before amortization	(24,659)	(22,710)	(49,316)	(44,518)																										(7,792)	(10,549)	(16,337)	(15,410)
General and administrative	(5,764)	(5,385)	(11,164)	(10,659)																										(920)	(38)	(1,716)	(1,022)
Depreciation and Amortization	2,882	2,736	5,754	5,590																										(8,876)	(9,943)	(22,772)	(18,006)
Net Loss																														616	(6,165)	(1,435)	(9,537)
Company's share of net income (loss)																														$ 3,111	$ 726	$ 5,451	$ (647)