Stockholders' Equity - Summary of Purchase and Sale of Common Stock (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Equity [Abstract]
Shares of common stock purchased	10,390	8,220	11,530
Aggregate purchase price of shares purchased	$ 700,234	$ 390,542	$ 291,349
Shares of common stock sold	37,086	4,717	10,694
Aggregate sale price of shares sold	$ 2,777,630	$ 271,417	$ 322,928