Income Taxes (Schedule Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Income Taxes [Abstract]
Customers’ advances for construction	$ 27,009	$ 28,845
Costs expensed for book not deducted for tax, principally accrued expenses	23,585	28,211
Post-retirement benefits		5,186
Tax effect of regulatory liabilities for post-retirement benefits	26,453	16,080
Tax attribute and credit carryforwards	235,838	243,131
Operating lease liabilities	13,558	16,064
Unrecovered purchased gas costs	4,654
Other	10,248	7,586
Total gross deferred tax assets	341,345	345,103
Less valuation allowance	(38,940)	(36,662)
Net deferred tax assets	302,405	308,441
Utility plant, principally due to depreciation and differences in the basis of fixed assets due to variation in tax and book accounting	1,495,526	1,510,752
Deferred taxes associated with the gross-up of revenues necessary to recover, in rates, the effect of temporary differences	128,975	179,825
Post-retirement benefits	6,130
Utility plant acquisition adjustment basis differences	198	222
Deferred investment tax credit	5,092	5,406
Operating lease right-of-use assets	12,250	14,034
Over-recovered purchased gas costs		4,739
Total gross deferred tax liabilities	1,648,171	1,714,978
Net deferred tax liability	$ 1,345,766	$ 1,406,537