Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Significant Accounting Policies [Abstract]
Capitalized development and construction salaries and other related costs	$ 0.6	$ 0.5
Maximum period after cessation of major construction activity that projects are considered complete	1 year