Employee Benefits - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2015 USD ($) Agreement Participants	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Defined Contribution Profit Sharing Plan And Retirement Savings 401 (k) Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Maximum contributions employees may contribute	$ 18,000
Employer contributions charged to expense	$ 414,000	$ 341,000	$ 302,000
Pentegra Defined Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Identification Number	135645888
Plan number	333
Number of collective bargaining agreements | Agreement	0
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 | Participants	59
Pentegra Defined Benefit Plan [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of contributions to plan	5.00%