Premises, Equipment and Lease Commitments - Additional Information (Detail) $ in Thousands		1 Months Ended	3 Months Ended	9 Months Ended	12 Months Ended
	Dec. 19, 2014 USD ($) parking_stall	Jan. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2015 USD ($) Facility	Dec. 31, 2014 USD ($)
Schedule of Operating Leases [Line Items]
Depreciation expense				$ 1,900	$ 2,900	$ 2,400
Number of facilities leased (in facilities) | Facility					18
Operating lease expiration year					2029
Land and building lease rental expense				1,300	$ 1,900	1,800
Building acquired, purchase price		$ 4,000
Recorded gain from the sale of the branch				(3)	1,676	1,328
Lease termination expense				0	1,454	$ 0
Number of stall parking ramp (in parking stalls) | parking_stall	261
Transaction closing date on purchase agreement						Dec. 19, 2014
Gain (loss) from the sale of deposits	$ 1,400			$ 0	0	$ 6,392
Lease term						9 years
Deferred gain (loss) related to disposition						$ 6,400
Deferred gain recognized during the period					1,400	$ 59
Appleton Branch
Schedule of Operating Leases [Line Items]
Recorded gain from the sale of the branch			$ 1,400		1,400
Menasha and Madison Branches
Schedule of Operating Leases [Line Items]
Lease termination expense					$ 1,500
Minimum
Schedule of Operating Leases [Line Items]
Non-cancelable operating lease remaining term						1 year