LOAN PORTFOLIO - Corporation's TDR Activity (Parenthetical) (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Financing Receivable Modifications [Line Items]
Loans held for investment transferred to held for sale	$ 1,775	$ 67,937
TDR [Member] \| Commercial Portfolio Segment [Member] \| Construction Loans [Member]
Financing Receivable Modifications [Line Items]
Charge Offs Loans Held For Sale		5,100
Loans held for investment transferred to held for sale		$ 30,000

Amount, before tax, of (gain) loss recognized for the (reversal of write-down) write-down to fair value, less cost to sell, of a disposal group. Excludes discontinued operations.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration