Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
U.S. federal income tax rate		21.00%
Tax reform adjustments to provision for income taxes	$ 0
Federal net operating loss carryforward expiration year		2033
State net operating loss carryforward expiration year		2019
Valuation allowance related to tax law changes	2,300,000		$ 2,300,000
Interest and penalties associated with unrecognized tax benefits				$ 100,000
Accrued interest and penalties associated with unrecognized tax benefits	200,000	$ 300,000	200,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
State NOL carryforwards	3,400,000		3,400,000	0
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards		734,900,000
Portion of state NOL carryforwards, not able to be utilized before expiration	608,900,000	698,400,000	608,900,000	536,000,000
Valuation allowance for deferred assets associated with carryforwards	$ 31,000,000	34,200,000	31,000,000
Deferred tax assets valuation allowance		2,961,000	4,112,000	$ 7,651,000
Federal [Member]
Operating Loss Carryforwards [Line Items]
Deferred tax assets valuation allowance		2,739,000	$ 14,604,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Gross tax credits		$ 8,100,000
Tax carryforward period		20 years
Tax credit carryforward expiration year		2034
Alternative minimum tax (ATM) remaining federal tax NOL carryforwards		$ 611,000,000