v3.24.0.1
Income Taxes (Tables)
12 Months Ended
Dec. 31, 2023
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:
202320222021
Current:
Federal
$281.2 $72.4 $234.9 
State
108.5 81.5 67.3 
Deferred:
Federal
72.3 164.2 (34.1)
State
29.1 16.9 18.6 
Uncertain tax positions and interest and other(31.0)8.9 (3.9)
Provision for income taxes$460.1 $343.9 $282.8 
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:
202320222021
Federal statutory rate21.0 %21.0 %21.0 %
State income taxes, net of federal benefit4.4 4.6 4.5 
Non-deductible expenses1.2 1.1 1.0 
Uncertain tax position taxes and interest(0.8)0.2 0.1 
Investment tax credits(4.0)(7.6)(8.0)
Other, net(0.8)(0.5)(0.6)
Effective income tax rate21.0 %18.8 %18.0 %
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:
20232022
Deferred tax liabilities relating to:
Differences between book and tax basis of property and equipment
$(1,229.4)$(1,252.7)
Difference between book and tax basis of intangible assets
(582.8)(521.7)
Operating right-of-use lease assets
(59.3)(74.3)
Basis difference due to redemption of partnership interests
(81.8)(82.0)
Total liabilities
$(1,953.3)$(1,930.7)
Deferred tax assets relating to:
Environmental reserves
$235.9 $253.0 
Accruals not currently deductible
104.6 94.6 
Net operating loss carryforwards
75.1 88.5 
Difference between book and tax basis of other assets
14.1 14.4 
Operating right-of-use lease liabilities
59.9 80.5 
Other
17.5 15.2 
Total assets
507.1 546.2 
Valuation allowance
(48.6)(43.1)
Net deferred tax asset
458.5 503.1 
Net deferred tax liabilities$(1,494.8)$(1,427.6)
Schedule of changes in the deferred tax valuation allowance
Changes in the deferred tax valuation allowance for the years ended December 31 follow:
202320222021
Valuation allowance, beginning of year$43.1 $43.7 $43.8 
Additions charged to provision for income taxes3.3 1.9 0.4 
Deferred tax assets realized or written-off0.3 (6.4)0.1 
Other, net1.9 3.9 (0.6)
Valuation allowance, end of year$48.6 $43.1 $43.7 
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:
202320222021
Balance at beginning of year$111.0 $101.5 $101.1 
Additions for tax positions of current year1.2 7.1 — 
Additions for tax positions of prior years2.6 2.4 0.5 
Reductions for tax positions of prior years(7.5)— (0.1)
Reductions for tax positions resulting from lapse of statute of limitations(0.1)— — 
Settlements(65.7)— — 
Balance at end of year$41.5 $111.0 $101.5