Summary of Significant Accounting Policies Supplemental Disclosures Related to Consolidated Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Supplemental cash flow information
Total interest costs incurred	$ 53,736	$ 55,418	$ 53,487
Interest capitalized	1,488	1,570	1,551
Interest expense	52,248	53,848	51,936
Cash paid for interest, net of amounts capitalized	52,632	47,473	47,793
Cash paid for income taxes	462	461	641
Supplemental schedule of noncash investing and financing activities
Increase (decrease) in accounts payable and accrued liabilities for construction in progress	8,379	(2,746)	(435)
Increase (decrease) in accrued leasing commissions	3,534	726	(355)
Reduction to capital for prepaid equity financing costs	$ 241	$ 0	$ 0