Income Taxes (Tables)

12 Months Ended

Dec. 31, 2021

Income Tax Disclosure [Abstract]

Schedule of components of the provision for income taxes

The components of the provision for income taxes for the years ended December 31 follow:

	2021		2020		2019
Current:
Federal	$	234.9	$	71.7	$	46.1
State	67.3		43.6		40.5
Deferred:
Federal	(34.1)		65.4		151.8
State	18.6		12.6		18.9
State deferred benefit - change in valuation allowance	—		(17.2)		(4.6)
Uncertain tax positions and interest, and other	(3.9)		(3.0)		(30.7)
Provision for income taxes	$	282.8	$	173.1	$	222.0

Schedule of reconciliations of the statutory federal income tax rate to our effective tax rate

The reconciliations of the statutory federal income tax rate to our effective tax rate for the years ended December 31 follow:

	2021		2020		2019
Federal statutory rate	21.0	%	21.0	%	21.0	%
State income taxes, net of federal benefit	4.5		4.5		4.2
Change in valuation allowance	—		(1.5)		(0.4)
Non-deductible expenses	1.0		1.7		1.7
Uncertain tax position taxes and interest	0.1		0.1		(0.3)
Investment tax credits	(8.0)		(8.8)		(6.5)
Other, net	(0.6)		(1.8)		(2.6)
Effective income tax rate	18.0	%	15.2	%	17.1	%

Schedule of components of the net deferred income tax asset and liability

The components of the net deferred income tax asset and liability as of December 31 follow:

	2021		2020
Deferred tax liabilities relating to:
Differences between book and tax basis of property and equipment	$	(949.2)	$	(1,010.7)
Difference between book and tax basis of intangible assets	(503.7)		(464.6)
Operating right-of-use lease assets	(66.5)		(60.9)
Basis difference due to redemption of partnership interests	(82.2)		(85.3)
Total liabilities	$	(1,601.6)	$	(1,621.5)
Deferred tax assets relating to:
Environmental reserves	$	217.6	$	224.6
Accruals not currently deductible	82.4		84.5
Net operating loss carryforwards	105.1		111.8
Difference between book and tax basis of other assets	22.5		21.7
Operating right-of-use lease liabilities	66.4		61.1
Other	14.1		13.3
Total assets	508.1		517.0
Valuation allowance	(43.7)		(43.8)
Net deferred tax asset	464.4		473.2
Net deferred tax liabilities	$	(1,137.2)	$	(1,148.3)

Schedule of changes in the deferred tax valuation allowance

Changes in the deferred tax valuation allowance for the years ended December 31 follow:

	2021		2020		2019
Valuation allowance, beginning of year	$	43.8	$	67.6	$	73.5
Additions charged to provision for income taxes	0.4		2.2		0.1
Deferred tax assets realized or written-off	0.1		(28.3)		(6.0)
Other, net	(0.6)		2.3		—
Valuation allowance, end of year	$	43.7	$	43.8	$	67.6

Schedule of activity in our gross unrecognized tax benefits

The following table summarizes the activity in our gross unrecognized tax benefits for the years ended December 31:

	2021		2020		2019
Balance at beginning of year	$	101.1	$	100.7	$	104.9
Additions for tax positions of prior years	0.5		0.4		0.9
Reductions for tax positions of prior years	(0.1)		—		—
Reductions for tax positions resulting from lapse of statute of limitations	—		—		(0.2)
Settlements	—		—		(4.9)
Balance at end of year	$	101.5	$	101.1	$	100.7