ALLOWANCE FOR LOAN AND LEASE LOSSES - Changes in Allowance for Loan and Lease Losses (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	$ 222,395	$ 285,858
Charge-offs	(32,013)	(53,707)
Recoveries	2,712	2,712
Provision For Loan Lease And Other Losses	32,970	31,915
Ending balance	226,064	266,778
Balance at end of period	62,140	85,016	55,205	102,601
Ending balance: general allowance	163,924	181,762
Ending balance	9,485,372	9,566,785	9,262,436
Ending balance: impaired loans	954,981	879,388	945,407	919,112
Ending balance: purchased credit-impaired loans	181,114		102,604
Ending balance: loans with general allowance	8,349,277	8,684,014
Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit-impaired loans	0	0
Ending balance: purchased credit-impaired loans	181,114	3,383
Residential Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	27,301	33,110
Charge-offs	(5,192)	(6,422)
Recoveries	98	69
Provision For Loan Lease And Other Losses	6,475	3,751
Ending balance	28,682	30,508
Balance at end of period	14,862	17,273
Ending balance: general allowance	13,820	13,235
Ending balance	3,331,620	2,548,101
Ending balance: impaired loans	429,526	419,308
Ending balance: loans with general allowance	2,724,493	2,128,793
Residential Mortgage [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit-impaired loans	0	0
Ending balance: purchased credit-impaired loans	177,601	0
Commercial Mortgage [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	50,894	73,138
Charge-offs	(4,006)	(5,810)
Recoveries	276	35
Provision For Loan Lease And Other Losses	(2,137)	(851)
Ending balance	45,027	66,512
Balance at end of period	13,238	29,833
Ending balance: general allowance	31,789	36,679
Ending balance	1,649,263	1,846,016
Ending balance: impaired loans	224,365	219,860
Ending balance: loans with general allowance	1,421,619	1,626,156
Commercial Mortgage [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit-impaired loans	0	0
Ending balance: purchased credit-impaired loans	3,279	0
Commercial And Industrial Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	63,721	85,295
Charge-offs	(4,453)	(22,459)
Recoveries	558	663
Provision For Loan Lease And Other Losses	10,353	16,091
Ending balance	70,179	79,590
Balance at end of period	24,871	19,098
Ending balance: general allowance	45,308	60,492
Ending balance	2,442,867	2,947,837
Ending balance: impaired loans	226,656	151,653
Ending balance: loans with general allowance	2,216,211	2,796,184
Commercial And Industrial Loans [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit-impaired loans	0	0
Ending balance: purchased credit-impaired loans	0	0
Construction Loans [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	12,822	35,814
Charge-offs	(605)	(970)
Recoveries	207	617
Provision For Loan Lease And Other Losses	1,215	(8,050)
Ending balance	13,639	27,411
Balance at end of period	3,381	15,154
Ending balance: general allowance	10,258	12,257
Ending balance	124,440	152,579
Ending balance: impaired loans	37,593	58,636
Ending balance: loans with general allowance	86,847	93,943
Construction Loans [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit-impaired loans	0	0
Ending balance: purchased credit-impaired loans	0	0
Consumer Loan [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Beginning balance	67,657	58,501
Charge-offs	(17,757)	(18,046)
Recoveries	1,573	1,328
Provision For Loan Lease And Other Losses	17,064	20,974
Ending balance	68,537	62,757
Balance at end of period	5,788	3,658
Ending balance: general allowance	62,749	59,099
Ending balance	1,937,182	2,072,252
Ending balance: impaired loans	36,841	29,931
Ending balance: loans with general allowance	1,900,107	2,038,938
Consumer Loan [Member] | Purchased Credit Impaired [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Ending balance: purchased credit-impaired loans	0	0
Ending balance: purchased credit-impaired loans	$ 234	$ 3,383