Summary Of Significant Accounting Policies (Accumulated Other Comprehensive Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended			6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012	Jun. 30, 2013		Jun. 30, 2012	Dec. 31, 2012
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax	$ (6,500)			$ (6,500)			$ (6,867)
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans Net Unamortized (Gain) Loss, Tax	(3,500)			(3,500)			(3,698)
Other income-net	681		405	1,562		1,427
Tax expense	(15,412)		(10,360)	(40,648)		(31,498)
Net of tax	25,730		18,532	68,831		56,745
Accumulated Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities, Tax	(668)			(668)			99
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	(1,136)			(1,136)			167
Accumulated other comprehensive loss	(7,636)			(7,636)			(6,700)
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Other income-net	16			18
Total before tax	16			18
Tax expense	(6)			(7)
Net of tax	10			11
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(282)			(565)
Tax expense	(99)			(198)
Net of tax	(183)			(367)
Amortization of net loss	(4,891)	[1]		(9,782)	[1]
Adjustment due to effects of regulation	$ 4,609	[1]		$ 9,217	[1]

[1] These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 6 for additional details).