Summary of Significant Accounting Policies Construction in Progress (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Construction in Progress [Line Items]
Internal direct construction costs capitalized related to development of properties and land holdings	$ 5,200,000	$ 3,700,000	$ 4,700,000
Capitalized interest	4,800,000	2,600,000	2,600,000
Salaries including bonuses and benefits, capitalized during the period	5,194,000	3,673,000	4,669,000
Development [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	1,749,000	156,000	57,000
Redevelopment [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	184,000	194,000	353,000
Tenant Improvements [Member]
Construction in Progress [Line Items]
Salaries including bonuses and benefits, capitalized during the period	$ 3,261,000	$ 3,323,000	$ 4,259,000