Income Taxes (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of income tax expense (benefit) from continuing operations

Income tax (benefit) expense is summarized as follows:

	Years Ended December 31,
	2017			2016			2015
	(Thousands)
Current:
Federal	$	(65,034	)	$	(82,905	)	$	85,696
State	27			(298		)	1,103
Subtotal	(65,007		)	(83,203		)	86,799
Deferred:
Federal	(998,483		)	(117,155		)	(109,642		)
State	(52,129		)	(63,106		)	127,518
Subtotal	(1,050,612		)	(180,261		)	17,876
Total income taxes	$	(1,115,619	)	$	(263,464	)	$	104,675

Schedule of reconciliation of income tax expense to amount computed at the federal statutory rate

Income tax (benefit) expense differed from amounts computed at the federal statutory rate of 35% on pre-tax income as follows:

	Years Ended December 31,
	2017			2016			2015
	(Thousands)
Tax at statutory rate	$	259,884		$	(138,084	)	$	149,296
Federal tax reform	(1,205,140		)	—			—
State income taxes	(52,606		)	(71,613		)	(7,566		)
Valuation allowance	10,680			23,808			91,144
Noncontrolling partners’ share of earnings	(122,365		)	(112,672		)	(82,850		)
Regulatory liability/asset	10,488			35,438			(35,438		)
Federal tax credits	(34,956		)	(4,539		)	(7,243		)
Other	18,396			4,198			(2,668		)
Income tax (benefit) expense	$	(1,115,619	)	$	(263,464	)	$	104,675
Effective tax rate	(150.2		)%	66.8		%	24.5		%

Schedule of reconciliation of the beginning and ending amount of reserve for uncertain tax positions(excluding interest and penalties)

The following table reconciles the beginning and ending amount of reserve for uncertain tax positions (excluding interest and penalties): 

	2017			2016			2015
	(Thousands)
Balance at January 1	$	252,434		$	259,301		$	56,957
Additions based on tax positions related to current year	50,469			23,978			152,983
Additions for tax positions of prior years	8,978			20,336			50,688
Reductions for tax positions of prior years	(10,323		)	(51,181		)	(1,327		)
Lapse of statute of limitations	—			—			—
Balance at December 31	$	301,558		$	252,434		$	259,301

Summary of source and tax effects of temporary differences between financial reporting and tax bases of assets and liabilities

The following table summarizes the source and tax effects of temporary differences between financial reporting and tax bases of assets and liabilities:

	As of December 31,
	2017			2016
	(Thousands)
Deferred income taxes:
Total deferred income tax assets	$	(971,184	)	$	(875,303	)
Total deferred income tax liabilities	2,740,084			2,635,307
Total net deferred income tax liabilities	1,768,900			1,760,004
Total deferred income tax liabilities (assets):
Drilling and development costs expensed for income tax reporting	2,074,091			1,473,355
Tax depreciation in excess of book depreciation	644,590			1,161,952
Incentive compensation and deferred compensation plans	(43,822		)	(77,743		)
Net operating loss carryforwards	(564,180		)	(282,943		)
Investment in partnerships	(132,667		)	(386,676		)
Alternative minimum tax credit carryforward	(435,190		)	(224,428		)
Federal tax credits	(50,341		)	(2,508		)
Unrealized hedge (losses) gains	21,403			(101,430		)
Other	(7,376		)	(997		)
Total excluding valuation allowances	1,506,508			1,558,582
Valuation allowances	262,392			201,422
Total net deferred income tax liabilities	$	1,768,900		$	1,760,004