Pension And Other Postretirement Benefits (Schedule Of Changes In Fair Value Of Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	$ 658.4	$ 658.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	658.4
Balance, end of year	722.0	658.4
Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	416.5	416.5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	416.5
Balance, end of year	437.1	416.5
Quoted Prices in Active Markets for Identical Inputs (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	219.5	219.5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	219.5
Balance, end of year	259.7	219.5
Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	25.2	10.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	22.4	10.4
Realized gains/(losses)		0.1
Unrealized gains/(losses)	1.6	1.5
Purchases	2.5	11.2
Sales	(1.3)	(0.8)
Balance, end of year	25.2	22.4
Equity Securities - U.S.
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	40.0	40.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	40.0
Balance, end of year	47.9	40.0
Equity Securities - U.S. | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	14.0	14.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	14.0
Balance, end of year	17.3	14.0
Equity Securities - U.S. | Quoted Prices in Active Markets for Identical Inputs (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	26.0	26.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	26.0
Balance, end of year	30.6	26.0
Equity Securities - International
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	58.6	58.6
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	58.6
Balance, end of year	70.3	58.6
Equity Securities - International | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	20.7	20.7
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	20.7
Balance, end of year	24.9	20.7
Equity Securities - International | Quoted Prices in Active Markets for Identical Inputs (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	37.9	37.9
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	37.9
Balance, end of year	45.4	37.9
Fixed Income Investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	447.9	447.9
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	447.9
Balance, end of year	479.9	447.9
Fixed Income Investments | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	312.7	312.7
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	312.7
Balance, end of year	317.4	312.7
Fixed Income Investments | Quoted Prices in Active Markets for Identical Inputs (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	135.2	135.2
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	135.2
Balance, end of year	162.5	135.2
Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	32.0	32.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	32.0
Balance, end of year	36.0	32.0
Hedge Funds | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	32.0	32.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	32.0
Balance, end of year	36.0	32.0
Private Markets
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	28.0	28.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	28.0
Balance, end of year	29.4	28.0
Private Markets | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	17.0	17.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	17.0
Balance, end of year	15.6	17.0
Private Markets | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	13.8	6.0
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	11.0	6.0
Realized gains/(losses)		0.1
Unrealized gains/(losses)	1.0	0.7
Purchases	2.5	4.4
Sales	(0.7)	(0.2)
Balance, end of year	13.8	11.0
Other
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	49.5	49.5
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	49.5
Balance, end of year	54.7	49.5
Other | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	17.7	17.7
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	17.7
Balance, end of year	22.1	17.7
Other | Quoted Prices in Active Markets for Identical Inputs (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	20.4	20.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	20.4
Balance, end of year	21.2	20.4
Other | Significant Unobservable Inputs (Level 3)
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	11.4	4.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	11.4	4.4
Realized gains/(losses)
Unrealized gains/(losses)	0.6	0.8
Purchases		6.8
Sales	(0.6)	(0.6)
Balance, end of year	11.4	11.4
Short-term Investments
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	2.4	2.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	2.4
Balance, end of year	3.8	2.4
Short-term Investments | Investments Measured at NAV [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan fair value of plan assets measured at net asset value	2.4	2.4
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Balance, beginning of year	2.4
Balance, end of year	$ 3.8	$ 2.4