Debt Financing Debt Financing Schedule of Long Term Debt (Details) - USD ($) $ in Thousands | Sep. 30, 2016 | Dec. 31, 2015 |
Debt Instrument [Line Items] | | |
Debt, Principal Outstanding | $ 2,492,858 | $ 2,557,744 |
Unamortized Premium/ (Discount) | 25 | 105 |
Unamortized Deferred Financing Fees | (9,459) | (12,193) |
Notes Payable | $ 2,483,424 | 2,545,656 |
Revolving Credit Facility- Revolving Loan [Member] | | |
Debt Instrument [Line Items] | | |
Credit facility, Interest Rate (percent) | 2.13% | |
Credit facility, principal outstanding | $ 322,000 | 327,000 |
Revolving Credit Facility- Term Loan [Member] | | |
Debt Instrument [Line Items] | | |
Credit facility, Interest Rate (percent) | 2.08% | |
Credit facility, principal outstanding | $ 495,000 | 495,000 |
Brindleyplace JV [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.11% | |
Debt, Principal Outstanding | $ 157,006 | 179,197 |
Southpark [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 5.67% | |
Debt, Principal Outstanding | $ 18,000 | 18,000 |
Fifty South Sixth [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.12% | |
Debt, Principal Outstanding | $ 125,000 | 125,000 |
Flagship Capital Joint Venture [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Credit facility, Interest Rate (percent) | 4.25% | |
Credit facility, principal outstanding | $ 512 | 14,943 |
One Hundred Brookes Street [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 4.09% | |
Debt, Principal Outstanding | $ 32,998 | 31,546 |
Poland Logistics Portfolio [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.00% | |
Debt, Principal Outstanding | $ 68,106 | 67,601 |
Minneapolis Retail Center [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 3.50% | |
Debt, Principal Outstanding | $ 65,500 | 65,500 |
Eight Twenty Five Ann [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.32% | |
Debt, Principal Outstanding | $ 61,861 | 59,139 |
Mercedes Benz Bank [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 1.28% | |
Debt, Principal Outstanding | $ 37,454 | 36,719 |
465 Victoria [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.97% | |
Debt, Principal Outstanding | $ 40,619 | 38,831 |
New City [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.30% | |
Debt, Principal Outstanding | $ 78,344 | 83,978 |
One Westferry Circus [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 3.30% | |
Debt, Principal Outstanding | $ 62,251 | 71,050 |
The Campus at Playa Vista [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 1.93% | |
Debt, Principal Outstanding | $ 150,000 | 150,000 |
Perspective Defense [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.20% | |
Debt, Principal Outstanding | $ 78,477 | 76,342 |
Fiege Mega Centre [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 1.40% | |
Debt, Principal Outstanding | $ 25,588 | 25,135 |
55 M Street [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 1.98% | |
Debt, Principal Outstanding | $ 72,000 | 72,000 |
25 Cabot Square [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 3.50% | |
Debt, Principal Outstanding | $ 160,491 | 183,175 |
Simon Hegele Logistics [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 1.90% | |
Debt, Principal Outstanding | $ 39,725 | 38,940 |
818 Bourke [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.37% | |
Debt, Principal Outstanding | $ 66,988 | 64,952 |
The Summit [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.08% | |
Debt, Principal Outstanding | $ 170,000 | 170,000 |
Harder Logistics Portfolio [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 0.95% | |
Debt, Principal Outstanding | $ 77,348 | 76,106 |
Water Wall Place [Member] | Construction Loan Payable [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.13% | |
Debt, Principal Outstanding | $ 44,897 | 44,897 |
Aviva Coral Gables JV [Member] | Construction Loan Payable [Member] | | |
Debt Instrument [Line Items] | | |
Effective interest rate (percent) | 2.52% | |
Debt, Principal Outstanding | $ 42,693 | $ 42,693 |
Minimum [Member] | Flagship Capital Joint Venture [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Variable interest rate, floor (percent) | 4.25% | |