Property Dispositions and Assets Held for Sale (Assets Held-for-Sale) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total other assets held for sale, net	$ 0	$ 9,815
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total real estate assets held for sale, net	0	225,939
Straight-line rent receivables	0	2,059
Prepaid expenses and other assets	0	454
Deferred lease costs, less accumulated amortization of $0 and $2,825 as of September 30, 2017 and December 31, 2016, respectively	0	7,302
Accumulated amortization on deferred lease costs	0	2,825
Total other assets held for sale, net	0	9,815
Disposal Group, Held-for-sale, Not Discontinued Operations | Land
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate assets held for sale, net:	0	52,710
Disposal Group, Held-for-sale, Not Discontinued Operations | Building and building improvements
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate assets held for sale, net:	0	173,218
Accumulated depreciation (building improvements)	0	88,319
Disposal Group, Held-for-sale, Not Discontinued Operations | Construction in progress
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Real estate assets held for sale, net:	$ 0	$ 11