Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 19, 2012
Income Taxes [Line Items]
Net income (loss)		$ 25,882,000	$ 201,700,000	$ (61,833,000)
Income tax expense or benefit		$ 0	$ 0	$ 0
Income tax at the federal statutory rate		35.00%	35.00%	35.00%
Income tax paid		$ 0	$ 0	$ 0
Reduction of deferred tax asset		$ 842,900,000
Valuation allowance equal to net deferred federal income tax asset		100.00%	100.00%	100.00%
Abandoned stock					$ 8,400,000,000
Available and utilizable NOL carry forward		$ 6,021,010,000
NOLs expiration date		2031
Capital loss carryforward expiration year			2017
Capital loss carryforward subject to expiration year		2018
Reserves for uncertain federal income tax positions		$ 0
Income tax interest income, expense or penalties		$ 0	$ 0	$ 0
Income tax examination, year under examination		2011
ASU 2016-09 [Member]
Income Taxes [Line Items]
Excess tax benefits against income tax expenses recognized in income		$ 2,900,000
Capital Loss Carryforward [Member]
Income Taxes [Line Items]
Capital loss carryforward			150,000,000
Capital Loss Expired in 2017
Income Taxes [Line Items]
Capital loss carryforward			$ 148,300,000
Capital Loss Subject to Expiration in 2018
Income Taxes [Line Items]
Capital loss carryforward		$ 1,600,000
Scenario Forecast [Member]
Income Taxes [Line Items]
Income tax at the federal statutory rate	21.00%