Operations and Significant Accounting Policies - Supplemental Statement of Cash Flows Information - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021
Supplemental Cash Flow Information [Abstract]
Cash Paid for Interest – Net of Amounts Capitalized		$ 35.6	$ 33.8
Noncash Investing and Financing Activities [Abstract]
Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment		3.1	(8.8)
Reclassification of Property, Plant and Equipment to Inventory	[1]	78.6	0.0
Capitalized Asset Retirement Costs		8.8	3.5
AFUDC–Equity		$ 1.7	$ 1.1

[1] The decommissioning of the existing Northern Wind assets resulted in a reclassification from Property, Plant and Equipment – Net to Inventories – Net in the second quarter of 2022 as they are being sold to a subsidiary of Xcel Energy Inc.