Commitments and Contingencies - Schedule of FHLB Borrowings (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance	$ 26,000	$ 33,000
Rate	2.44%	2.25%
January 10, 2019 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance		$ 7,000
Rate		1.55%
Maturity		Jan. 10, 2019
Eleventh July Two Thousand Nineteen [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance	$ 5,000	$ 5,000
Rate	2.56%	2.56%
Maturity	Jul. 11, 2019	Jul. 11, 2019
January 10, 2020 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance	$ 5,000	$ 5,000
Rate	1.73%	1.73%
Maturity	Jan. 10, 2020	Jan. 10, 2020
July 10, 2020 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance	$ 5,000	$ 5,000
Rate	2.84%	2.84%
Maturity	Jul. 10, 2020	Jul. 10, 2020
October 6, 2020 [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance	$ 5,000	$ 5,000
Rate	1.92%	1.92%
Maturity	Oct. 06, 2020	Oct. 06, 2020
Twenty Sixth July Two Thousand Twenty Three [Member]
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Outstanding Balance	$ 6,000	$ 6,000
Rate	3.01%	3.01%
Maturity	Jul. 26, 2023	Jul. 26, 2023