LOANS HELD FOR INVESTMENT - Loan Portfolio Held for Investment (Parenthetical) (Detail) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Loans held for investment	$ 11,950,932	$ 11,552,825
Unaccreted fair value net purchase discounts	25,800	29,300
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Loans held for investment	3,030,954	2,886,263
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member] \| Commercial loans secured by real estate [Member]
Loans held for investment	$ 807,600	$ 838,500

Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479344/326-20-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 3B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479319/326-20-50-5

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant