ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in Allowance for Loan and Lease Losses (Detail) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		$ 173,485	$ 234,454	$ 205,603	$ 240,710
Charge-offs		(19,369)	(46,566)	(107,751)	(101,467)
Recoveries		1,741	4,679	14,467	11,285
Provision For Loan Lease And Other Losses		75,013	21,503	118,551	63,542
Ending balance		230,870	214,070	230,870	214,070
Balance at end of period		48,155	72,682	48,155	72,682
Allowance for loan losses Purchased Credit Impaired		10,235	6,857	10,235	6,857
Ending balance: general allowance		172,480	134,531	172,480	134,531
Ending balance		8,877,214	8,863,654	8,877,214	8,863,654
Ending balance: impaired loans		779,259	912,854	779,259	912,854	$ 735,625	$ 887,905	$ 953,774	$ 806,509
Ending balance: purchased credit-impaired loans		157,794	168,141	157,794	168,141
Ending balance: loans with general allowance		7,940,161	7,782,659	7,940,161	7,782,659
Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses Purchased Credit Impaired	[1]	10,235	6,857	10,235	6,857
Residential Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		40,587	38,955	33,980	39,570
Charge-offs		(7,177)	(8,514)	(22,369)	(27,352)
Recoveries		321	972	1,961	2,159
Provision For Loan Lease And Other Losses		23,321	4,553	43,480	21,589
Ending balance		57,052	35,966	57,052	35,966
Balance at end of period		19,417	9,667	19,417	9,667
Ending balance: general allowance		27,772	19,661	27,772	19,661
Ending balance		3,274,340	3,299,942	3,274,340	3,299,942
Ending balance: impaired loans		425,835	444,039	425,835	444,039
Ending balance: purchased credit-impaired loans		153,609	165,014	153,609	165,014
Ending balance: loans with general allowance		2,694,896	2,690,889	2,694,896	2,690,889
Residential Mortgage [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses Purchased Credit Impaired	[1]	9,863	6,638	9,863	6,638
Commercial Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		38,576	69,799	57,261	68,211
Charge-offs		(266)	(13,730)	(32,123)	(15,742)
Recoveries		43	335	151	414
Provision For Loan Lease And Other Losses		17,590	(152)	30,654	3,369
Ending balance		55,943	56,252	55,943	56,252
Balance at end of period		10,456	25,907	10,456	25,907
Ending balance: general allowance		45,115	30,126	45,115	30,126
Ending balance		1,601,638	1,545,014	1,601,638	1,545,014
Ending balance: impaired loans		153,875	198,500	153,875	198,500
Ending balance: purchased credit-impaired loans		4,185	3,127	4,185	3,127
Ending balance: loans with general allowance		1,443,578	1,343,387	1,443,578	1,343,387
Commercial Mortgage [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses Purchased Credit Impaired	[1]	372	219	372	219
Commercial And Industrial Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		42,082	69,789	61,953	68,768
Charge-offs		(738)	(10,587)	(19,168)	(16,260)
Recoveries		114	929	5,613	1,885
Provision For Loan Lease And Other Losses		(1,079)	5,597	(8,019)	11,335
Ending balance		40,379	65,728	40,379	65,728
Balance at end of period		11,240	28,668	11,240	28,668
Ending balance: general allowance		29,139	37,060	29,139	37,060
Ending balance		2,144,236	2,167,011	2,144,236	2,167,011
Ending balance: impaired loans		110,939	178,174	110,939	178,174
Ending balance: purchased credit-impaired loans		0	0	0	0
Ending balance: loans with general allowance		2,033,297	1,988,837	2,033,297	1,988,837
Commercial And Industrial Loans [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses Purchased Credit Impaired	[1]	0	0	0	0
Construction Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		3,736	2,747	2,562	3,519
Charge-offs		(47)	(19)	(705)	(623)
Recoveries		16	140	594	301
Provision For Loan Lease And Other Losses		242	2,480	1,496	2,151
Ending balance		3,947	5,348	3,947	5,348
Balance at end of period		1,865	3,004	1,865	3,004
Ending balance: general allowance		2,082	2,344	2,082	2,344
Ending balance		129,460	124,298	129,460	124,298
Ending balance: impaired loans		50,373	47,707	50,373	47,707
Ending balance: purchased credit-impaired loans		0	0	0	0
Ending balance: loans with general allowance		79,087	76,591	79,087	76,591
Construction Loans [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses Purchased Credit Impaired	[1]	0	0	0	0
Consumer Loan [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance		48,504	53,164	49,847	60,642
Charge-offs		(11,141)	(13,716)	(33,386)	(41,490)
Recoveries		1,247	2,303	6,148	6,526
Provision For Loan Lease And Other Losses		34,939	9,025	50,940	25,098
Ending balance		73,549	50,776	73,549	50,776
Balance at end of period		5,177	5,436	5,177	5,436
Ending balance: general allowance		68,372	45,340	68,372	45,340
Ending balance		1,727,540	1,727,389	1,727,540	1,727,389
Ending balance: impaired loans		38,237	44,434	38,237	44,434
Ending balance: purchased credit-impaired loans		0	0	0	0
Ending balance: loans with general allowance		1,689,303	1,682,955	1,689,303	1,682,955
Consumer Loan [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Allowance for loan losses Purchased Credit Impaired	[1]	$ 0	$ 0	$ 0	$ 0

[1] Refer to Note 7- "Loans Held For Investment-PCI Loans" for additional information about changes in the allowance for loan losses related to PCI loans.