Income Taxes (Tables)

12 Months Ended

Sep. 30, 2017

Income Tax Disclosure [Abstract]

Provisions for Income Taxes

The provisions for income taxes consist of the following:

	2017			2016			2015
Current expense (benefit):
Federal	$	(12,253	)	$	(17,845	)	$	34,990
State	5,739			6,805			15,138
Total current (benefit) expense	(6,514		)	(11,040		)	50,128
Deferred expense (benefit):
Federal	70,293			71,005			28,877
State	8,593			6,262			815
Investment tax credit amortization	(318		)	(329		)	(336		)
Total income tax expense	$	72,054		$	65,898		$	79,484

Reconciliation from US Federal Statutory Tax Rate to Effective Tax Rate

A reconciliation from the U.S. federal statutory tax rate to our effective tax rate is as follows:

	2017		2016		2015
U.S. federal statutory tax rate	35.0	%	35.0	%	35.0	%
Difference in tax rate due to:
State income taxes, net of federal benefit	5.0		5.2		5.1
Excess tax benefits on share-based payments	(0.9	)	—		—
Other, net	(0.8	)	0.2		(0.5	)
Effective tax rate	38.3	%	40.4	%	39.6	%

Deferred Tax Liabilities (Assets)

Deferred tax liabilities (assets) comprise the following at September 30:

	2017			2016
Excess book basis over tax basis of property, plant and equipment	$	564,327		$	491,038
Goodwill	49,588			45,070
Derivative financial instruments	—			948
Regulatory assets	136,093			149,660
Other	3,140			2,910
Gross deferred tax liabilities	753,148			689,626
Pension plan liabilities	(57,011		)	(74,129		)
Allowance for doubtful accounts	(1,681		)	(1,637		)
Deferred investment tax credits	(1,224		)	(1,356		)
Employee-related expenses	(6,793		)	(5,247		)
Regulatory liabilities	(12,780		)	(16,798		)
Environmental liabilities	(22,224		)	(22,757		)
Derivative financial instruments	(354		)	—
Other	(15,616		)	(17,473		)
Gross deferred tax assets	(117,683		)	(139,397		)
Net deferred tax liabilities	$	635,465		$	550,229

Reconciliation of Unrecognized Tax Benefits

A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows:

	2017			2016		2015
Unrecognized tax benefits – beginning of year	$	2,055		$	—	$	—
Additions for tax positions taken in prior years	604			2,055		—
Additions for tax positions of the current year	—			—		—
Settlements with tax authorities/statute lapses	(830		)	—		—
Unrecognized tax benefits – end of year	$	1,829		$	2,055	$	—