Employee Benefits - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2019 USD ($) Participant Agreement	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	72-1532188
Pentegra Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	13-5645888
Plan number	333
Number of collective bargaining agreements | Agreement	0
Pentegra Defined Benefit Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of contributions to plan	5.00%
Pentegra Defined Benefit Plan [Member] | First Independence Corporation and Subsidiary [Member]
Defined Benefit Plan Disclosure [Line Items]
Number of participants retaining benefits under the plan | Participant	54
Defined Contribution Profit Sharing Plan And Retirement Savings 401 (k) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum contributions employees may contribute	$ 19,000
Employer contributions charged to expense	$ 826,000	$ 885,000	$ 704,000