Fair Value Measurements (Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	$ 693.0	$ 728.9
Other investments	2.4	2.2
Assets, Fair Value Disclosure, Excluding Netting Adjustments	695.4	731.1
Netting agreements	(584.5)	(607.4)
Assets, Collateral/Margin Received or Paid	4.2	79.4
Assets from price risk management, total	112.7	42.1
Total assets at fair value	115.1	44.3
Liabilities from price risk management	644.9	713.2
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	644.9	713.2
Netting agreements	(584.5)	(607.4)
Liabilities, Collateral/Margin Received or Paid	(23.5)	(8.8)
Liabilities from price risk management, total	36.9	114.6
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	36.7	33.3
Other investments	2.4	2.2
Assets, Fair Value Disclosure, Excluding Netting Adjustments	39.1	35.5
Liabilities from price risk management	49.7	26.9
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	49.7	26.9
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	656.3	695.6
Other investments	0.0	0.0
Assets, Fair Value Disclosure, Excluding Netting Adjustments	656.3	695.6
Liabilities from price risk management	595.2	686.3
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	595.2	686.3
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	0.0	0.0
Other investments	0.0	0.0
Assets, Fair Value Disclosure, Excluding Netting Adjustments	0.0	0.0
Liabilities from price risk management	0.0	0.0
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	$ 0.0	$ 0.0