Co-investments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	$ 716,443		$ 677,133
Balance sheets [Abstract]
Rental properties and real estate under development	308,266		50,430
Other liabilities	22,281		22,189
Statement of operations [Abstract]
Interest expense	(26,055)	(25,211)
General and administrative	(7,075)	(6,239)
Equity income in co-investments	10,526	4,211
Depreciation and Amortization	(2,986)	(2,930)
Membership interest in Wesco I [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	136,495		142,025
Membership interest in Wesco III [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	38,928		39,073
Partnership interest in Fund II [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	7,235		4,166
Membership interest in a limited liability company that owns Expo [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	11,877		12,041
Total operating co-investments [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	194,535		197,305
Membership interests in limited liability companies with CPPIB that own and are developing Epic, Connolly Station, Mosso I & II, Park 20, and The Village [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	336,417		301,538
Membership interests in limited liability companies that own and are developing The Huxley and The Dylan [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	19,151		18,545
Membership interests in limited liability companies that owns and is developing One South Market [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	22,632		17,115
Total development co-investments [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	378,200		337,198
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	95,115		94,711
Preferred return rate (in hundredths)	10.10%
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	15,955		15,775
Preferred return rate (in hundredths)	9.50%
Preferred interest in a related party limited liability company that owns Madison Park at Anaheim with a preferred return of 9% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	13,824		13,824
Preferred return rate (in hundredths)	9.00%
Preferred interest in related party limited liability company that owns an apartment development in Redwood City with a preferred return of 12% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	9,681		9,455
Preferred return rate (in hundredths)	12.00%
Preferred interest in a limited liability company that owns an apartment development in San Jose with a preferred return of 12% [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	9,133		8,865
Preferred return rate (in hundredths)	12.00%
Total preferred interest investments [Member]
Investments in joint ventures accounted for under the equity method of accounting [Abstract]
Total co-investment	143,708		142,630
Total co investment [Member]
Balance sheets [Abstract]
Rental properties and real estate under development	1,993,763		1,953,328
Other assets	131,716		61,578
Total assets	2,125,479		2,014,906
Debt	756,117		667,641
Other liabilities	82,519		125,479
Equity	1,286,843		1,221,786
Total liabilities and equity	2,125,479		2,014,906
Company's share of equity	716,443		677,133
Statement of operations [Abstract]
Property revenues	27,960	27,859
Property operating expenses	(11,560)	(9,828)
Net property operating income	16,400	18,031
Gain on sale of real estate	11,369	0
Interest expense	(6,023)	(6,778)
General and administrative	(1,388)	(1,514)
Equity income in co-investments	4,759	0
Depreciation and Amortization	(10,693)	(11,019)
Net (loss) income	14,424	(1,280)
Company's share of net income	$ 10,526	$ 4,211