Debt - Narrative (Details)								1 Months Ended	3 Months Ended		4 Months Ended	6 Months Ended	9 Months Ended
	Apr. 28, 2020 USD ($) $ / shares	Apr. 28, 2020 USD ($) $ / shares	Apr. 28, 2020 USD ($) numberOfWells $ / shares	Apr. 28, 2020 USD ($) d $ / shares	Apr. 23, 2020 $ / shares	Feb. 03, 2020	Jan. 21, 2020 USD ($)	Aug. 31, 2020 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) $ / shares	Sep. 30, 2019 USD ($)	Aug. 01, 2020	Apr. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)
Line of Credit Facility
Redemption price, percentage		100.00%
Payment of debt premium charges	$ 32,500,000
Proceeds from issuance of debt													$ 2,250,000,000	$ 1,000,000,000
Repayment of borrowing on credit facility													1,822,250,000	2,900,250,000
Convertible note, measurement period trading days | d				5
Convertible notes, measurement period consecutive trading days | d				5
Strike price (in dollars per share) | $ / shares	$ 15.00	$ 15.00	$ 15.00	$ 15.00
Capped price (in dollars per share) | $ / shares	$ 18.75	$ 18.75	$ 18.75	$ 18.75
Convertible notes impact on shareholders equity									$ 63,600,000				63,645,000
Senior Notes
Line of Credit Facility
Additional interest rate limit															2.00%
Surety Bond
Line of Credit Facility
Surety bonds issued, amount													93,000,000
Term Loan Agreement | Unsecured Debt
Line of Credit Facility
Average daily balance of short-term loans outstanding during the period												$ 692,000,000
Weighted average interest rates of average daily balance of short-term loans											3.30%	2.60%
Face amount									1,000,000,000.0	$ 1,000,000,000.0	$ 1,000,000,000.0		1,000,000,000.0	1,000,000,000.0
Repayments of debt							$ 200,000,000
Repayment of borrowing on credit facility	$ 450,000,000
Senior Notes Due February 2025 | Senior Notes
Line of Credit Facility
Face amount							$ 1,000,000,000.0
Interest rate, stated percentage							6.125%								7.875%
Senior Notes Due February 2030 | Senior Notes
Line of Credit Facility
Face amount							$ 750,000,000
Interest rate, stated percentage							7.00%								8.75%
Floating Rate Notes Due 2020 | Senior Notes
Line of Credit Facility
Repayments of debt							$ 500,000,000
Redemption price, percentage						100.00%
Interest expense, debt							$ 1,200,000
2.50 Senior Notes Due 2020 | Senior Notes
Line of Credit Facility
Interest rate, stated percentage							2.50%
Repayments of debt							$ 500,000,000
Redemption price, percentage							100.446%
Interest expense, debt							$ 4,200,000
Redemption premium							$ 2,200,000
Senior Notes Due November 2021 | Senior Notes
Line of Credit Facility
Interest rate, stated percentage							4.875%
Repayments of debt							$ 500,000,000
Interest expense, debt							7,400,000	$ 1,100,000
Payments to repurchase senior notes							517,400,000	105,900,000
Early tender premium							$ 10,000,000.0	3,300,000
Repurchase amount								$ 101,500,000								$ 4,600,000
1.75% Senior Notes Due 2026 | Senior Notes
Line of Credit Facility
Face amount	$ 500,000,000	$ 500,000,000	$ 500,000,000	$ 500,000,000
Interest rate, stated percentage	1.75%	1.75%	1.75%	1.75%
Redemption price, percentage		130.00%
Interest expense, debt									$ 7,270,000				$ 12,217,000
Offering cost	$ 16,900,000	$ 16,900,000	$ 16,900,000	$ 16,900,000
Proceeds from issuance of debt	$ 450,600,000
Convertible notes, trading days			20	20
Convertible notes, consecutive trading days			30	30
Minimum trigger price as percentage		98.00%
Convertible notes, conversion ratio													66.6667
Initial conversion price (in dollars per share) | $ / shares									$ 15.00				$ 15.00
Conversion premium, percent					20.00%
Convertible closing price (in dollars per share) | $ / shares					$ 12.50
Convertible notes, term													6 years
Effective interest rate									8.40%				8.40%
Fair value of convertible notes									$ 358,100,000				$ 358,100,000
Net deferred tax liability of convertible notes									41,000,000.0				41,000,000.0
Equity component of convertible notes									100,900,000				100,900,000
Debt issuance cost attributable to liability component									12,100,000				12,100,000
Debt issuance cost attributable to equity component									4,800,000				4,800,000
Unamortized discount									134,000,000.0				134,000,000.0
Unamortized Debt Issuance Expense									11,600,000				11,600,000
Credit Facility | EQT 2.5 Billion Facility
Line of Credit Facility
Line of credit facility, maximum borrowing capacity									2,500,000,000				2,500,000,000
Letters of credit outstanding under revolving credit facility									800,000,000				800,000,000				$ 0
Maximum amount of outstanding short-term loans at any time during the period									399,000,000	319,000,000			399,000,000	1,108,000,000
Average daily balance of short-term loans outstanding during the period									$ 149,000,000	$ 105,000,000			$ 90,000,000	$ 340,000,000
Weighted average interest rates of average daily balance of short-term loans									2.20%	3.60%			2.50%	4.00%
Credit Facility | EQT 2.5 Billion Facility | Base Rate
Line of Credit Facility
Basis spread on variable rate													1.00%
Credit Facility | EQT 2.5 Billion Facility | Eurodollar
Line of Credit Facility
Basis spread on variable rate													2.00%