Common Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended
	Nov. 30, 2019	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Common Equity [Line Items]
Proceeds from issuance of common stock, net		$ 6.4		$ 6.0	$ 234.8	$ 60.6
Equity Forward Agreements [Member]
Common Equity [Line Items]
Common stock to be issued, equity forward agreements (in shares)	4,275,127
Forward sales price (in dollars per share)	$ 52.235		$ 51.98
Proceeds from issuance of common stock, net			$ 222.0
Common stock issued during the period, equity forward agreements (in shares)			4,275,127		4,275,127