Fair Value Measurements (Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) - Fair Value, Measurements, Recurring - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	$ 909.7	$ 728.9
SPH units	2.5	2.2
Assets, Fair Value Disclosure, Excluding Netting Adjustments	912.2	731.1
Netting agreements	(816.5)	(607.4)
Assets, Collateral/Margin Received or Paid	(67.7)	(79.4)
Assets from price risk management, total	25.5	42.1
Total assets at fair value	28.0	44.3
Liabilities from price risk management	929.9	713.2
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	929.9	713.2
Netting agreements	(816.5)	(607.4)
Liabilities, Collateral/Margin Received or Paid	(5.8)	(8.8)
Liabilities from price risk management, total	107.6	114.6
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	53.3	33.3
SPH units	2.5	2.2
Assets, Fair Value Disclosure, Excluding Netting Adjustments	55.8	35.5
Liabilities from price risk management	62.3	26.9
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	62.3	26.9
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets from price risk management	856.4	695.6
SPH units	0.0	0.0
Assets, Fair Value Disclosure, Excluding Netting Adjustments	856.4	695.6
Liabilities from price risk management	867.6	686.3
Liabilities, Fair Value Disclosure, Excluding Netting Adjustments	867.6	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
SPH units	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