Consolidated Statements of Cash Flows - Supplemental Information (Supplemental Information) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Supplemental Cash Flow Elements [Abstract]
Interest paid, net of amounts capitalized	$ 14,267	$ 13,775
Non-Cash Transactions:
Ground lease right-of-use assets and associated liabilities	56,294	0
Common stock dividends declared	30,492	27,315
Change in accrued property, acquisition, development, and tenant expenditures	11,085	28,465
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