Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Income tax benefit	$ (498,859,000)	$ (47,219,000)	$ 40,099,000	$ 5,688,000	$ (68,784,000)	$ 24,137,000	$ (28,518,000)	$ 42,676,000	$ (500,291,000)	$ (30,489,000)	$ (251,026,000)
Deferred tax liabilities	160,196,000				666,668,000				160,196,000	666,668,000
Accrued interest or penalties related to tax amounts	0								$ 0
Minimum
Income Taxes [Line Items]
Period during which net operating loss carryforwards and alternative minimum tax expire									Dec. 31, 2020
Maximum
Income Taxes [Line Items]
Period during which net operating loss carryforwards and alternative minimum tax expire									Dec. 31, 2037
State
Income Taxes [Line Items]
Valuation allowances	158,296,000				101,372,000				$ 158,296,000	101,372,000
Federal
Income Taxes [Line Items]
Valuation allowances	32,530,000				$ 18,975,000				32,530,000	$ 18,975,000
Federal and State
Income Taxes [Line Items]
Net operating loss carryforwards	2,100,000,000								2,100,000,000
Net operating loss carryforward subject to expiration	1,400,000,000								1,400,000,000
Net operating loss carryforward not subject to expiration	712,800,000								712,800,000
Pennsylvania
Income Taxes [Line Items]
Net operating loss carryforwards	856,300,000								$ 856,300,000
Pennsylvania | Minimum
Income Taxes [Line Items]
Period during which net operating loss carryforwards and alternative minimum tax expire									Dec. 31, 2027
Pennsylvania | Maximum
Income Taxes [Line Items]
Period during which net operating loss carryforwards and alternative minimum tax expire									Dec. 31, 2038
Louisiana
Income Taxes [Line Items]
Net operating loss carryforwards	$ 561,100,000								$ 561,100,000
Louisiana | Minimum
Income Taxes [Line Items]
Period during which net operating loss carryforwards and alternative minimum tax expire									Dec. 31, 2034
Louisiana | Maximum
Income Taxes [Line Items]
Period during which net operating loss carryforwards and alternative minimum tax expire									Dec. 31, 2039