Annual report pursuant to Section 13 and 15(d)

Rentals Under Operating Leases (Details)

v2.4.1.9
Rentals Under Operating Leases (Details) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Operating Leased Assets [Line Items]      
2015 $ 192,105us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableCurrent    
2016 176,751us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInTwoYears    
2017 156,837us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInThreeYears    
2018 134,039us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInFourYears    
2019 112,575us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableInFiveYears    
Thereafter 316,645us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableThereafter    
Operating Leases, Future Minimum Payments Receivable 1,088,952us-gaap_OperatingLeasesFutureMinimumPaymentsReceivable    
Reimbursement income $ 31,610us-gaap_TenantReimbursements $ 26,822us-gaap_TenantReimbursements $ 25,528us-gaap_TenantReimbursements
Multifamily Properties [Member]      
Operating Leased Assets [Line Items]      
Lessee Leasing Arrangements, Operating Leases, Term of Contract 1 year