Acquisition and Divestiture Activity - Schedule of Acquired Loan Data (Detail) - Anchor BanCorp Wisconsin Inc [Member] $ in Thousands	Mar. 31, 2017 USD ($)
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	$ 1,637,806
Acquired Receivables Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	20,174
Gross Contractual Amounts Receivable at Acquisition Date	29,544
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	6,153
Acquired Receivables Not Subject to ASC 310-30 [Member]
Loans at Acquisition Date [Line Items]
Fair Value of Acquired Loans at Acquisition Date	1,617,632
Gross Contractual Amounts Receivable at Acquisition Date	2,143,532
Best Estimate at Acquisition Date of Contractual Cash Flows Not Expected to be Collected	$ 274,155

Loans at Acquisition Date [Line Items]

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- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the best estimate at the acquisition date of the contractual cash flows not expected to be collected, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the fair value of the receivables acquired, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the gross contractual amounts receivable, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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Period Type:	instant

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