Consolidated Statements of Cash Flows - Supplemental Information (Supplemental Cash Flows Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of amounts capitalized	$ 38,062	$ 43,166	$ 30,572
Income taxes paid	0	0	0
Non-Cash Transactions:
Non-cash assets and liabilities assumed in TIER transaction	1,512,373	0	0
Transfer from operating properties and related liabilities to assets and liabilities of real estate assets held for sale	318,516	0	0
Ground lease right-of-use assets and associated liabilities	56,294	0	0
Transfer from investment in unconsolidated joint venture to operating properties	50,781	0	68,498
Common stock dividends declared and accrued	42,559	27,326	25,202
Change in accrued property acquisition, development, and tenant asset expenditures	4,891	(18,104)	5,965
Non-cash consideration for property acquisition	10,071	0	0
Transfer from projects under development to operating properties	0	325,490	58,928
Cumulative effect of change in accounting principle	0	22,329	0
Transfer from investment in unconsolidated joint ventures to projects under development	$ 0	$ 7,025	$ 0