Income Tax (tables)

9 Months Ended

Sep. 30, 2013

Income Tax Disclosure [Abstract]

Effective Tax Rate Reconciliation

	Nine Months Ended September 30,
	2013		2012
Federal statutory tax rate	35.0	%	35.0	%
Increase (decrease):
Current state income tax, net of federal tax benefit	4.6		4.5
Amortization of investment and energy tax credits	(0.3	)	(0.3	)
Differences required to be flowed-through by regulatory commissions	2.2		1.4
Gains on company and trust-owned life insurance	(1.3	)	(1.2	)
One-time state tax adjustment, net of federal benefit	—		4.8
Other, net	0.6		0.9
Effective income tax rate	40.8	%	45.1	%