Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Components of Income Tax Expense from Continuing Operations

The following table summarizes the components of income tax expense for the years ended December 31:

	2017			2016			2015
Current income taxes
State	$	25		$	20		$	10
Federal	(1		)	1			—
Total current income taxes	$	24		$	21		$	10
Deferred income taxes
State	$	50		$	24		$	32
Federal	413			258			265
Amortization of deferred investment tax credits	(1		)	(1		)	(1		)
Total deferred income taxes	462			281			296
Provision for income taxes	$	486		$	302		$	306

Reconciliation of Income Tax Expense from Continuing Operations

The following is a reconciliation between the statutory federal income tax rate and the Company’s effective tax rate for the years ended December 31:

	2017		2016		2015
Income tax at statutory rate	35.0	%	35.0	%	35.0	%
Increases (decreases) resulting from:
State taxes, net of federal taxes	5.4	%	3.8	%	3.6	%
Tax Cuts and Jobs Act	13.7	%	—	%	—	%
Other, net	(0.8	)%	0.4	%	0.5	%
Effective tax rate	53.3	%	39.2	%	39.1	%

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:

	2017			2016
Deferred tax assets
Advances and contributions	$	395		$	540
Tax losses and credits	256			301
Regulatory income tax assets	327			—
Pension and other postretirement benefits	96			173
Other	49			90
Total deferred tax assets	1,123			1,104
Valuation allowance	(13		)	(6		)
Total deferred tax assets, net of allowance	$	1,110		$	1,098
Deferred tax liabilities
Property, plant and equipment	$	2,489		$	3,339
Deferred pension and other postretirement benefits	69			126
Other	103			229
Total deferred tax liabilities	2,661			3,694
Total deferred tax liabilities, net of deferred tax assets	$	(1,551	)	$	(2,596	)

Changes in Gross Liability Excluding Interest and Penalties for Unrecognized Tax Benefits

The following table summarizes the changes in the Company’s gross liability, excluding interest and penalties, for unrecognized tax benefits:

Balance as of January 1, 2016	$	233
Increases in current period tax positions	10
Decreases in prior period measurement of tax positions	(74		)
Balance as of December 31, 2016	$	169
Increases in current period tax positions	8
Decreases in prior period measurement of tax positions	(71		)
Balance as of December 31, 2017	$	106

Changes in Valuation Allowance

The following table summarizes the changes in the Company’s valuation allowance:

Balance as of January 1, 2015	$	10
Decreases in current period tax positions	(2		)
Balance as of December 31, 2015	$	8
Decreases in current period tax positions	(2		)
Balance as of December 31, 2016	$	6
Increases in current period tax positions	7
Balance as of December 31, 2017	$	13