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Additional Information Regarding Methods used to Evaluate Loan Portfolio for Impairment (Detail) - Additional Information Loan Portfolio - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans Receivable, Individually evaluated for impairment | $ 80,557 | $ 48,252
Loans Receivable, Collectively evaluated for impairment | 38,278,465 | 37,302,187
Total loans, net | 38,359,022 | 39,054,334
Acquired loans with deteriorated credit quality |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans Receivable, other |  | 1,703,895
Mortgage Receivable |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans Receivable, Individually evaluated for impairment | 31,747 | 29,660
Loans Receivable, Collectively evaluated for impairment | 36,278,241 | 35,402,029
Total loans, net | 36,309,988 | 37,046,444
Mortgage Receivable | Acquired loans with deteriorated credit quality |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans Receivable, other |  | 1,614,755
Other loans |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans Receivable, Individually evaluated for impairment | 48,810 | 18,592
Loans Receivable, Collectively evaluated for impairment | 2,000,224 | 1,900,158
Total loans, net | $ 2,049,034 | 2,007,890
Other loans | Acquired loans with deteriorated credit quality |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans Receivable, other |  | $ 89,140

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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=84173941&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were individually 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=84173941&loc=SL6953423-111524 + Details
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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 + Details
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