ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	$ 196,362	$ 231,843
Charge-offs	(28,360)	(29,360)
Recoveries	3,910	2,829
Provision (release)	11,820	20,544
Ending balance	183,732	225,856
Ending balance: specific reserve for impaired loans	50,554	56,930	$ 53,976
Ending balance	8,996,816	8,695,890	8,858,123
Ending balance: impaired loans	732,871	746,280	760,269	$ 790,308
General Allowance [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	131,032
Ending balance	121,824	157,675
Ending balance	8,119,502	7,794,329	7,951,214
PCI loans
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit impaired loans	11,354	11,251	11,354	11,251
Ending balance	144,443	155,281	146,640	$ 158,174
Residential Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	50,794	58,975
Charge-offs	(6,173)	(3,371)
Recoveries	626	335
Provision (release)	6,639	447
Ending balance	51,886	56,386
Ending balance: specific reserve for impaired loans	20,753	22,546	19,965
Ending balance	3,126,562	3,267,868	3,163,208
Ending balance: impaired loans	393,735	417,610
Residential Portfolio Segment [Member] \| General Allowance [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	19,875
Ending balance	20,179	22,967
Ending balance	2,591,848	2,699,191	2,616,300
Residential Portfolio Segment [Member] \| PCI loans
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit impaired loans	10,954	10,873	10,954
Ending balance	140,979	151,067	143,176
Commercial Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance	3,854,962		3,750,202
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	55,581	48,493
Charge-offs	(2,400)	(6,810)
Recoveries	128	49
Provision (release)	121	8,661
Ending balance	53,430	50,393
Ending balance: specific reserve for impaired loans	20,314	13,451	17,684
Ending balance	1,558,724	1,552,503	1,522,662
Ending balance: impaired loans	222,181	162,126	227,426
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| General Allowance [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	37,497
Ending balance	32,716	36,564
Ending balance	1,333,079	1,386,163	1,291,772
Commercial Portfolio Segment [Member] \| Mortgage Receivable [Member] \| PCI loans
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit impaired loans	400	378	400
Ending balance	3,464	4,214	3,464
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	32,546	48,871
Charge-offs	(6,311)	(1,930)
Recoveries	1,095	62
Provision (release)	(5,009)	656
Ending balance	22,321	47,659
Ending balance: specific reserve for impaired loans	4,112	14,375	9,693
Ending balance	2,211,731	2,061,773	2,148,111
Ending balance: impaired loans	82,347	119,778	91,192
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member] \| General Allowance [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	22,853
Ending balance	18,209	33,284
Ending balance	2,129,384	1,941,995	2,056,919
Commercial Portfolio Segment [Member] \| Commercial And Industrial Sector [Member] \| PCI loans
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit impaired loans	0	0	0
Ending balance	0	0	0
Consumer Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	53,849	70,982
Charge-offs	(13,269)	(12,072)
Recoveries	2,020	2,370
Provision (release)	10,164	6,016
Ending balance	52,764	67,296
Ending balance: specific reserve for impaired loans	4,779	5,074	5,874
Ending balance	2,015,292	1,734,596	1,944,713
Ending balance: impaired loans	28,428	34,699
Consumer Portfolio Segment [Member] \| General Allowance [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	47,975
Ending balance	47,985	62,222
Ending balance	1,986,864	1,699,897	1,913,387
Consumer Portfolio Segment [Member] \| PCI loans
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit impaired loans	0	0	0
Ending balance	0	0	0
Construction Loans [Member] \| Commercial Portfolio Segment [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	3,592	4,522
Charge-offs	(207)	(5,177)
Recoveries	41	13
Provision (release)	(95)	4,764
Ending balance	3,331	4,122
Ending balance: specific reserve for impaired loans	596	1,484	760
Ending balance	84,507	79,150	79,429
Ending balance: impaired loans	6,180	12,067
Construction Loans [Member] \| Commercial Portfolio Segment [Member] \| General Allowance [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	2,832
Ending balance	2,735	2,638
Ending balance	78,327	67,083	72,836
Construction Loans [Member] \| Commercial Portfolio Segment [Member] \| PCI loans
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit impaired loans	0	0	0
Ending balance	$ 0	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Reserve for loans impairments recorded after acquisition as a result of current information and events which result in it being probable that estimated cash flows will be less than previously expected or because actual cash flows are less than cash flows previously expected. This relates to loans not accounted for as debt securities, with evidence of deterioration of credit quality since origination that was acquired by completion of a transfer for which it is probable, at acquisition, that the investor will be unable to collect all contractually required payments receivable.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

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Amount of allowance for credit losses related to recorded investment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount of expense related to estimated loss from loan and lease transactions.

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