Income Taxes - Changes in Valuation Allowance for Deferred Tax Assets (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes Disclosure [Line Items]
Valuation allowance as of beginning of year	$ (83,434)	$ (54,773)	$ (33,826)
Valuation allowance as of end of year	(74,842)	(83,434)	(54,773)
Decreases Recorded as Benefit to Income Tax Provision [Member]
Income Taxes Disclosure [Line Items]
Decreases (increases) recorded as benefit to income tax provision	36,606	4,771	2,858
Decreases Recorded as Benefit to Equity [Member]
Income Taxes Disclosure [Line Items]
Decreases (increases) recorded as benefit to income tax provision	24,537
Increases Recorded to Income Tax Provision [Member]
Income Taxes Disclosure [Line Items]
Decreases (increases) recorded as benefit to income tax provision	$ (52,551)	$ (33,432)	$ (23,805)