Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 13, 2017
Tax Credit Carryforward [Line Items]
Federal tax reform benefit	$ 1,205,140	$ 0	$ 0
Alternative minimum tax credit carryforward	$ 435,190	$ 224,428
Federal statutory rate	35.00%	35.00%
Income tax expense from government regulated asset	$ 10,500
Tax benefit in connection with recent IRS guidance	1,115,619	$ 263,464	(104,675)
Effective tax rate, amount	120,500	102,000	94,100
DTA, decrease resulting from uncertain tax positions	300	500
Tax positions for which the ultimate deductibility is highly certain	4,700	5,500	6,400
Interest expense	3,200	1,600	1,600
Interests and penalties	8,400	5,200	3,600
Decrease in unrecognized tax benefits is reasonably possible	42,500
Valuation allowances		201,400
Deferred tax asset, NOL, state and local		81,500
Net operating loss carryforwards	564,180	282,943
Tax benefits as and addition to common stockholders' equity		900
Domestic Tax Authority
Tax Credit Carryforward [Line Items]
Operating loss carryforwards	194,300
Valuation allowances	22,900
State and Local Jurisdiction
Tax Credit Carryforward [Line Items]
Valuation allowances	217,000
Deferred tax asset, NOL, state and local	130,000
Net operating loss carryforwards	21,200
Valuation allowance	22,500
Rice Merger Agreement
Tax Credit Carryforward [Line Items]
Deferred income taxes				$ 1,106,000
Deferred Tax Assets
Tax Credit Carryforward [Line Items]
Uncertain tax positions	84,100	$ 75,400	114,200
Equitable Gas Company, LLC
Tax Credit Carryforward [Line Items]
Tax benefit in connection with recent IRS guidance			$ 35,400
Federal Marginal Well Tax Credit
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	30,200
Federal Marginal Well Tax Credit | Tax Year 2016
Tax Credit Carryforward [Line Items]
Tax credit carryforward, amount	$ 6,100