Deposits (Schedule of Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deposit [Line Items]
Non-interest-bearing demand deposits:	$ 15,117,051	$ 10,873,629
Time Deposits, $100,000 or More	809,395
Total Interest-bearing deposits	19,898,710	16,765,935
Total deposits	35,015,761	27,639,564
Commercial And Individual [Member]
Deposit [Line Items]
Non-interest-bearing demand deposits:	13,914,754	10,212,265
Correspondent Banks [Member]
Deposit [Line Items]
Non-interest-bearing demand deposits:	242,225	246,181
Public Funds [Member]
Deposit [Line Items]
Non-interest-bearing demand deposits:	960,072	415,183
Savings and interest checking	597,503	548,399
Money market accounts	50,070	73,180
Time Deposits, $100,000 or More	5,163	24,672
Time accounts under $100,000	25	25
Total Interest-bearing deposits	652,761	646,276
Private Accounts [Member]
Deposit [Line Items]
Savings and interest checking	9,132,789	7,147,327
Money market accounts	8,977,585	7,888,433
Time Deposits, $100,000 or More	804,232	736,481
Time accounts under $100,000	331,343	347,418
Total Interest-bearing deposits	$ 19,245,949	$ 16,119,659

Deposit [Line Items]

No definition available.

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- Definition

The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

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- Definition

Amount of deposits in accounts that offer many of the same services as checking accounts although transactions may be somewhat more limited, share some of the characteristics of a money market fund and are insured by the Federal government, also known as money market accounts.

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Amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts and money-market deposit accounts (MMDAs).

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The aggregate of all domestic and foreign interest-bearing deposit liabilities.

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The aggregate amount of all domestic and foreign noninterest-bearing deposits liabilities held by the entity.

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Amount of time deposit liabilities, including certificates of deposit, in denominations of $100,000 or more.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E

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Amount of time deposit liabilities, including certificates of deposit, in denominations of less than $100,000.

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