Segment Reporting Segment Reporting (Second Generation Capital Expenditures) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements	$ 59,349	$ 61,900	$ 98,821
Operating Segments [Member]
Segment Reporting Information [Line Items]
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements	59,349	61,900	98,821
Operating Segments [Member] | Industrial [Member]
Segment Reporting Information [Line Items]
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements	51,785	45,716	53,840
Operating Segments [Member] | Medical Office [Member]
Segment Reporting Information [Line Items]
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements	2,515	4,711	3,131
Operating Segments [Member] | Other Segments [Member]
Segment Reporting Information [Line Items]
Payments For Second Generation Tenant Improvements Leasing Costs And Building Improvements	$ 5,049	$ 11,473	$ 41,850