Real Estate Investments Summary of Co-Investments (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Co-investment		$ 1,036,411	$ 677,133
Century Towers [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment	27,000	12,000
Preferred Stock Dividend Rate Percentage In First Five Years	8.10%
Total operating co investments [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		607,790	360,616
Membership interest in Wesco I and III [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		188,404	181,098
Partnership interest in Fund II [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		696	4,166
Membership interest in a limited liability company that owns and is developing Expo [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		7,352	12,041
Membership interest in a limited liability company that owns The Huxley [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		11,471	11,224
Membership Interest In Limited Liability Company That Owns Connolly Station [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		46,653	45,242
Membership Interest In Epic [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		122,968	106,845
Membership interest in Wesco IV [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		86,289	0
Membership interest in BEXAEW [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		73,771	0
Membership Interest In Palm Valley [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		70,186	0
Total development co investments [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		319,930	173,887
Membership interests in limited liability companies that own and are developing Epic, Lync, Elkhorn, and Folsom and Fifth [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		268,016	149,451
Membership interests in limited liability companies that owns and is developing One South Market [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		30,919	17,115
Membership interests in limited liability companies that own and are developing The Huxley and The Dylan [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		7,874	7,321
Membership Interest In Limited Liability Company That Owns And Is Developing Century Towers [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		13,121	0
Total preferred interest investments [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		108,691	142,630
Membership interest in Wesco II that owns a preferred equity interest in Park Merced with a preferred return of 10.1 [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		0	94,711
Cumulative dividend 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]
Schedule of Equity Method Investments [Line Items]
Co-investment		16,571	15,775
Cumulative dividend 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]
Schedule of Equity Method Investments [Line Items]
Co-investment		13,824	13,824
Cumulative dividend 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]
Schedule of Equity Method Investments [Line Items]
Co-investment		10,396	9,455
Cumulative dividend rate (in hundredths)		12.00%
Preferred Interest, Extension Term		1 year
Preferred Interest, Number Of Extension Options		1
Preferred interest in related party limited liability company that owns an apartment development in San Jose with a preferred return of 12% [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		10,011	8,865
Cumulative dividend rate (in hundredths)		12.00%
Preferred interest in a limited liability company that owns 8th & Thomas with a preferred return of 10 [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		13,145	0
Cumulative dividend rate (in hundredths)		10.00%
Preferred Interest, Extension Term		1 year
Preferred Interest, Number Of Extension Options		1
Preferred interest in a limited liability company that owns Newbury Park with preferred return of 12 [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		13,150	0
Cumulative dividend rate (in hundredths)		12.00%
Preferred interest in a limited liability company that owns Century Towers with preferred return of 10 [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		12,357	0
Preferred interests in limited liability companies that own apartment communities in San Jose with preferred returns of 9% and 10% [Member]
Schedule of Equity Method Investments [Line Items]
Co-investment		$ 19,237	$ 0
Cumulative dividend rate (in hundredths)		9.00%