Summary of Quarterly Results - Summary of Quarterly Results of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Net interest income	$ 1,894	$ 1,724	$ 901	$ 417	$ 263	$ 55	$ 10,540	$ 788
Net other expenses	354	311	165	115	85	13	945	98
Net income	$ 1,540	$ 1,413	$ 736	$ 302	$ 178	$ 42	$ 3,991	$ 220
Per share information-basic and diluted
Net income per share of common stock	$ 0.51	$ 0.55	$ 0.41	$ 0.24	$ 0.20	$ 0.25	$ 1.84	$ 0.80
Weighted average common stock outstanding	3,026,364	2,551,864	1,780,663	1,256,174	901,821	171,417	2,165,753	274,482