Consolidated Statements of Cash Flows - Supplemental Information (Supplemental Cash Flows Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of amounts capitalized	$ 30,572	$ 32,215	$ 29,337
Income taxes paid	0	0	2
Non-Cash Transactions:
Transfer from investment in unconsolidated joint venture to operating properties	68,498	0	0
Transfer from projects under development to operating properties	58,928	0	121,709
Common stock dividends declared	25,202	0	0
Change in accrued property acquisition, development, and tenant asset expenditures	5,965	7,918	(2,483)
Non-cash assets and liabilities assumed in Merger	0	1,856,255	0
Non-cash assets and liabilities distributed in Spin-Off	0	(948,306)	0
Mortgage note payable legally defeased	0	20,170	0
Transfer from land held to projects under development	0	8,099	0
Transfer from investment in unconsolidated joint ventures to projects under development	0	5,880	0
Transfer from operating properties and related assets to real estate assets and other assets held for sale	0	0	7,246
Transfer from operating properties and related liabilities to liabilities of real estate assets held for sale	$ 0	$ 0	$ 1,347