Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax [Line Items]
Federal statutory income tax rate	21.00%	21.00%	35.00%
Provisional income tax expense (benefit)		$ 244,000	$ (18,900,000)
Tax credit carryforwards	$ 37,619,000	39,560,000
Income tax penalties and interest expense	0	$ 0	$ 0
Federal
Income Tax [Line Items]
Tax credit carryforwards	$ 37,600,000
Tax credit carryforwards, expiration start year	2037