Deposits (Schedule of Deposits) (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deposit [Line Items]
Non-interest-bearing demand deposits:	$ 10,270,233	$ 10,149,061
Total Interest-bearing deposits	14,073,362	13,986,869
Total deposits	24,343,595	24,135,930
Commercial And Individual [Member]
Deposit [Line Items]
Non-interest-bearing demand deposits:	9,251,463	9,256,045
Correspondent Banks [Member]
Deposit [Line Items]
Non-interest-bearing demand deposits:	378,930	429,000
Private Accounts [Member]
Deposit [Line Items]
Savings and interest checking	5,149,905	4,743,963
Money market accounts	7,536,998	7,860,403
Time accounts of $100,000 or more	420,697	490,209
Time accounts under $100,000	405,726	454,220
Total private accounts	13,513,326	13,548,795
Public Funds [Member]
Deposit [Line Items]
Non-interest-bearing demand deposits:	639,840	464,016
Savings and interest checking	420,324	326,090
Money market accounts	93,969	57,145
Time accounts of $100,000 or more	44,941	53,684
Time accounts under $100,000	802	1,155
Total public funds	$ 560,036	$ 438,074

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- Definition

Interest Bearing Deposits Public Funds

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- Definition

Interest Bearing Private Accounts Deposits

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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://www.xbrl.org/2003/role/presentationRef
-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=6876686&loc=d3e534808-122878

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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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- Definition

The aggregate amount of domestic time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $100,000 or more.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=50488274&loc=d3e64164-112818

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The aggregate amount of domestic or foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) that total to less than $100,000.

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