Segment Information (Details)	Mar. 31, 2012 Property Store	Mar. 31, 2011 Property Store
Company's combined shopping and office properties portfolios
Shopping centers owned	420	476
Office properties	4	5
Unconsolidated Joint Ventures [Member]
Company's combined shopping and office properties portfolios
Shopping centers owned	172	191
Consolidated Joint Ventures [Member]
Company's combined shopping and office properties portfolios
Shopping centers owned	2	3
States [Member]
Company's combined shopping and office properties portfolios
Shopping centers owned	38	41
Office properties	2	3