Summary Of Significant Accounting Policies (Other Expense (Income) - Net) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Interest income	$ (166)	$ (455)	$ (804)	$ (1,029)
Interest on regulatory deferrals	(19)	(15)	(43)	(83)
Equity-related AFUDC	(1,127)	(421)	(2,875)	(1,655)
Net loss on investments	2,430	560	2,957	597
Other expense	2,877	1,957	7,040	5,466
Other income	(186)		(1,169)	(235)
Total	$ 3,809	$ 1,626	$ 5,106	$ 3,061