Commitments And Contingencies - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loss Contingencies [Line Items]
Securities held to maturity, mortgaged related securities, pledged	$ 917,200	$ 346,000
Securities available for sale, other securities, pledged	388,000	840,700
Loans pledged to FHLB, collateral for wholesale borrowings	31,400,000	30,100,000
Commitments	2,543,065
Rental expense under non-cancelable operating lease and license agreements	33,600	33,200	$ 32,600
Rental income on bank-owned properties, netted in occupancy and equipment expense	9,900	9,500	$ 7,100
Total loan commitments
Loss Contingencies [Line Items]
Commitments	2,034,944	1,900,000
Commercial, performance stand-by, and financial stand-by letters of credit
Loss Contingencies [Line Items]
Commitments	$ 508,121	$ 339,400

Fair value portion of arrangements with third parties, including, but not limited to, operating lease arrangement and arrangement in which the entity has agreed to expend funds to procure goods or services, or has agreed to commit resources to supply goods or services.

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(25))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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The carrying amount as of the date of the latest financial statement presented of mortgage-related securities classified as held to maturity which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

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The carrying amount as of the date of the latest financial statement presented of other securities classified as available for sale or held for investment which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for FHLB debt obligations, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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Income earned by providing the use of assets to an outside party in exchange for a payment or series of payments that is nonoperating in nature.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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