Income Taxes (Tables)

12 Months Ended

Sep. 30, 2018

Income Tax Disclosure [Abstract]

Provisions for Income Taxes

The provisions for income taxes consist of the following:

	2018			2017			2016
Current expense (benefit):
Federal	$	(26,952	)	$	(12,253	)	$	(17,845	)
State	10,729			5,739			6,805
Total current (benefit) expense	(16,223		)	(6,514		)	(11,040		)
Deferred expense (benefit):
Federal	60,766			70,293			71,005
State	1,486			8,593			6,262
Investment tax credit amortization	(318		)	(318		)	(329		)
Total deferred expense	61,934			78,568			76,938
Total income tax expense	$	45,711		$	72,054		$	65,898

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:

	2018		2017		2016
U.S. federal statutory tax rate	24.5	%	35.0	%	35.0	%
Difference in tax rate due to:
State income taxes, net of federal benefit	4.7		5.0		5.2
Effect of tax rate changes - TCJA	(3.8	)	—		—
Excess tax benefits on share-based payments	(0.5	)	(0.9	)	—
Other, net	(1.4	)	(0.8	)	0.2
Effective tax rate	23.5	%	38.3	%	40.4	%

Deferred Tax Liabilities (Assets)

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

	2018			2017
Excess book basis over tax basis of property, plant and equipment	$	441,154		$	564,327
Goodwill	37,414			49,588
Derivative financial instruments	579			—
Regulatory assets	90,022			136,093
Other	3,375			3,140
Gross deferred tax liabilities	572,544			753,148
Pension plan liabilities	(19,831		)	(57,011		)
Allowance for doubtful accounts	(2,820		)	(1,681		)
Deferred investment tax credits	(760		)	(1,224		)
Employee-related expenses	(4,581		)	(6,793		)
Regulatory liabilities	(118,506		)	(12,780		)
Environmental liabilities	(14,551		)	(22,224		)
Derivative financial instruments	—			(354		)
Other	(10,571		)	(15,616		)
Gross deferred tax assets	(171,620		)	(117,683		)
Net deferred tax liabilities	$	400,924		$	635,465

Reconciliation of Unrecognized Tax Benefits

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

	2018			2017			2016
Unrecognized tax benefits – beginning of year	$	1,829		$	2,055		$	—
Additions for tax positions taken in prior years	6			604			2,055
Settlements with tax authorities/statute lapses	(1,147		)	(830		)	—
Unrecognized tax benefits – end of year	$	688		$	1,829		$	2,055