Consolidated Statements of Cash Flows - Supplemental Information (Supplemental Information) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of amounts capitalized	$ 22,130	$ 19,283
Non-Cash Transactions:
Non-cash assets and liabilities assumed in TIER transaction	1,512,384	0
Ground lease right-of-use assets and associated liabilities	56,294	0
Common stock dividends declared and accrued	42,563	27,326
Change in accrued property, acquisition, development, and tenant expenditures	8,973	24,121
Non-cash consideration for property acquisition	10,071	0
Transfers from projects under development to operating properties	0	212,628
Cumulative effect of change in accounting principle	0	22,329
Transfer from investment in unconsolidated joint venture to projects under development	$ 0	$ 7,025