Loans and Allowance for Loan Losses - Schedule of Receivables for which Contractually Required Payments would not be Collected (Parenthetical) (Detail)	3 Months Ended
Mar. 31, 2016
Anchor BanCorp Wisconsin Inc [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Effective date of acquisition	May 01, 2016

Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e845-128460

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Acquisition Date
-URI http://asc.fasb.org/extlink&oid=6919109

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=73531572&loc=d3e848-128460

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration