Additional Information Regarding Methods used to Evaluate Loan Portfolio for Impairment (Detail) - Additional Information Loan Portfolio - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, Individually evaluated for impairment	$ 66,234	$ 80,557
Loans Receivable, Collectively evaluated for impairment	39,352,523	38,278,465
Total loans, net	39,418,757	38,359,022
Mortgage Receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, Individually evaluated for impairment	20,886	31,747
Loans Receivable, Collectively evaluated for impairment	37,218,769	36,278,241
Total loans, net	37,239,655	36,309,988
Other loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Receivable, Individually evaluated for impairment	45,348	48,810
Loans Receivable, Collectively evaluated for impairment	2,133,754	2,000,224
Total loans, net	$ 2,179,102	$ 2,049,034

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.

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=84173941&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://fasb.org/us-gaap/role/ref/legacyRef
-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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