Goodwill and Other Intangible Assets - Additional Information (Detail) - USD ($)		3 Months Ended			6 Months Ended
	May 08, 2015	Jun. 30, 2016	Mar. 31, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Goodwill [Line Items]
Goodwill acquired during the period					$ 111,852,000	$ 57,619,000
Goodwill eliminated due to sale of insurance operations					41,000,000
Amortization expense of other intangible assets		$ 3,365,000		$ 2,977,000	6,012,000	6,058,000
Impairment charges					$ 0	$ 0
Core Deposits and Other Intangible Assets [Member] | Minimum [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships			5 years
Core Deposits and Other Intangible Assets [Member] | Maximum [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships			15 years
Customer Business Relationships [Member]
Goodwill [Line Items]
Intangible asset eliminated due to sale of insurance operations		6,500,000
Insurance Book of Business [Member] | Insurance [Member] | Customer Business Relationships [Member]
Goodwill [Line Items]
Estimated useful lives of core deposits and customer relationships					10 years
Increase (decrease) in intangible assets	$ 200,000		$ (200,000)
Anchor BanCorp Wisconsin Inc [Member]
Goodwill [Line Items]
Goodwill acquired during the period					$ 111,900,000
Anchor BanCorp Wisconsin Inc [Member] | Core Deposit [Member]
Goodwill [Line Items]
Increase (decrease) in intangible assets		$ 21,600,000