Income Taxes (Tables)
 12 Months Ended
Dec. 31, 2018
Income Tax Disclosure [Abstract]  
Components of Income Tax Expense from Continuing Operations
The following table provides the components of income tax expense for the years ended December 31:
 
2018
 
2017
 
2016
Current income taxes:
 
 
 
 
 
State
$
26

 
$
25

 
$
20

Federal
1

 
(1
)
 
1

Total current income taxes
$
27

 
$
24

 
$
21

Deferred income taxes:
 
 
 
 
 
State
$
33

 
$
50

 
$
24

Federal
163

 
413

 
258

Amortization of deferred investment tax credits
(1
)
 
(1
)
 
(1
)
Total deferred income taxes
195

 
462

 
281

Provision for income taxes
$
222

 
$
486

 
$
302
Reconciliation of Income Tax Expense from Continuing Operations
The following table provides a reconciliation between the statutory federal income tax rate and the Company’s effective tax rate for the years ended December 31:
 
2018
 
2017
 
2016
Income tax at statutory rate
21.0
%
 
35.0
 %
 
35.0
%
Increases (decreases) resulting from:
 
 
 
 
 
State taxes, net of federal taxes
5.5
%
 
5.4
 %
 
3.8
%
TCJA
1.5
%
 
13.7
 %
 
—
%
Other, net
0.2
%
 
(0.8
)%
 
0.4
%
Effective tax rate
28.2
%
 
53.3
 %
 
39.2
%
Components of Net Deferred Tax Liability from Continuing Operations
The following table provides the components of the net deferred tax liability as of December 31:
 
2018
 
2017
Deferred tax assets:
 
 
 
Advances and contributions
$
402

 
$
395

Tax losses and credits
131

 
196

Regulatory income tax assets
339

 
327

Pension and other postretirement benefits
91

 
96

Other
44

 
49

Total deferred tax assets
1,007

 
1,063

Valuation allowance
(14
)
 
(13
)
Total deferred tax assets, net of allowance
$
993

 
$
1,050

Deferred tax liabilities:
 
 
 

Property, plant and equipment
$
2,537

 
$
2,429

Deferred pension and other postretirement benefits
77

 
69

Other
97

 
103

Total deferred tax liabilities
2,711

 
2,601

Total deferred tax liabilities, net of deferred tax assets
$
(1,718
)
 
$
(1,551
)
Changes in Gross Liability Excluding Interest and Penalties for Unrecognized Tax Benefits
The following table provides the changes in gross liability, excluding interest and penalties, for unrecognized tax benefits:
 
Amount
Balance as of January 1, 2017
$
169

Increases in current period tax positions
8

Decreases in prior period measurement of tax positions
(71
)
Balance as of December 31, 2017
$
106

Increases in current period tax positions
13

Decreases in prior period measurement of tax positions
(22
)
Balance as of December 31, 2018
$
97
Changes in Valuation Allowance
The following table provides the changes in the valuation allowance:
 
Amount
Balance as of January 1, 2016
$
8

Decreases in current period tax positions
(2
)
Balance as of December 31, 2016
$
6

Decreases in current period tax positions
7

Balance as of December 31, 2017
$
13

Increases in current period tax positions
1

Balance as of December 31, 2018
$
14