Additional Information Regarding Methods used to Evaluate Loan Portfolio for Impairment (Detail) - Additional Information Loan Portfolio - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, Individually evaluated for impairment	$ 52,836	$ 48,252
Loans Receivable, Collectively evaluated for impairment	37,246,177	37,302,187
Total loans, net	38,903,954	39,054,334
Acquired loans with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, other	1,604,941	1,703,895
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, Individually evaluated for impairment	23,436	29,660
Loans Receivable, Collectively evaluated for impairment	35,346,837	35,402,029
Total loans, net	36,907,225	37,046,444
Mortgage Receivable \| Acquired loans with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, other	1,536,952	1,614,755
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, Individually evaluated for impairment	29,400	18,592
Loans Receivable, Collectively evaluated for impairment	1,899,340	1,900,158
Total loans, net	1,996,729	2,007,890
Other loans \| Acquired loans with deteriorated credit quality
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, other	$ 67,989	$ 89,140

Financing Receivable, Evaluated for Impairment

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The balance of financing receivables that were collectively evaluated for impairment.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

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- Definition

The balance of financing receivables that were individually evaluated for impairment.

+ References

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- Definition

Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.3)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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