Deposits - Schedule of Deposits (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Deposit [Line Items]
Total non-interest-bearing demand deposits	$ 14,845,770	$ 10,873,629
Interest-bearing Deposit Liabilities, Total	18,653,733	16,765,935
Total deposits	$ 33,499,503	$ 27,639,564
Total non-interest-bearing demand deposits, Percentage of Total	44.30%	39.30%
Percentage of Interest-bearing Domestic Deposits to Deposits	55.70%	60.70%
Total deposits, Percentage of Total	100.00%	100.00%
Commercial and Individual [Member]
Deposit [Line Items]
Total non-interest-bearing demand deposits	$ 13,852,404	$ 10,212,265
Total non-interest-bearing demand deposits, Percentage of Total	41.40%	36.90%
Correspondent Banks [Member]
Deposit [Line Items]
Total non-interest-bearing demand deposits	$ 208,836	$ 246,181
Total non-interest-bearing demand deposits, Percentage of Total	0.60%	0.90%
Private Accounts [Member]
Deposit [Line Items]
Savings and interest checking	$ 8,176,608	$ 7,147,327
Money market accounts	8,684,470	7,888,433
Time accounts of $100,000 or More	791,004	736,481
Time accounts under $100,000	339,174	347,418
Interest-bearing Deposit Liabilities, Total	$ 17,991,256	$ 16,119,659
Savings and interest checking, Percentage of Total	24.40%	25.90%
Money market accounts, Percentage of Total	25.90%	28.50%
Time accounts of $100,000 or more, Percentage of Total	2.40%	2.70%
Time accounts under $100,000, Percentage of Total	1.00%	1.20%
Percentage of Interest-bearing Domestic Deposits to Deposits	53.70%	58.30%
Public Funds [Member]
Deposit [Line Items]
Total non-interest-bearing demand deposits	$ 784,530	$ 415,183
Savings and interest checking	583,214	548,399
Money market accounts	76,088	73,180
Time accounts of $100,000 or More	3,092	24,672
Time accounts under $100,000	83	25
Interest-bearing Deposit Liabilities, Total	$ 662,477	$ 646,276
Total non-interest-bearing demand deposits, Percentage of Total	2.30%	1.50%
Savings and interest checking, Percentage of Total	1.80%	2.00%
Money market accounts, Percentage of Total	0.20%	0.30%
Time accounts of $100,000 or more, Percentage of Total	0.00%	0.10%
Time accounts under $100,000, Percentage of Total	0.00%	0.00%
Percentage of Interest-bearing Domestic Deposits to Deposits	2.00%	2.40%

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Deposits Percentage

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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.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The aggregate of all domestic and foreign interest-bearing deposit liabilities.

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Percentage of interest-bearing domestic deposit liabilities to total deposit liabilities.

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

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