Employee Benefit Plans (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / Family	Dec. 31, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)
Defined Benefit Plan Disclosure [Line Items]
401(k) deferred compensation and profit sharing plan, company contributions	$ 1,328	$ 1,121		$ 999
Annual losses per covered family | $ / Family	150,000
Annual deductible per covered family | $ / Family	255,000
Charges to earnings for self-insurance reserve	$ 4,192	3,153		2,666
Pension expense	$ 63	54
River Valley Bancorp | The Pentegra DB Plan
Defined Benefit Plan Disclosure [Line Items]
Total contributions under Defined Benefit Plan as reported on Form 5500			$ 153,186		$ 163,183
Multiemployer plan, maximum percentage of employer's contributions	5.00%
Postretirement Medical and Life Benefit Plan
Defined Benefit Plan Disclosure [Line Items]
Estimated future employer contributions in 2018	$ 84
Certain directors and officers
Defined Benefit Plan Disclosure [Line Items]
Accrued benefits payable	1,896	1,882
Deferred compensation expense	187	297		149
Certain officers
Defined Benefit Plan Disclosure [Line Items]
Accrued benefits payable	84	136
Deferred compensation expense	$ 48	$ 0		$ 215