LOANS AND ALLOWANCE FOR CREDIT LOSSES (Impaired Loans) (Details) (USD $)	6 Months Ended		12 Months Ended
	Jun. 30, 2014		Dec. 31, 2013
Loans and Leases Receivable Disclosure [Abstract]
Minimum amount for commercial non-accrual loans	$ 1,000,000
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, recorded investment	3,162,975,000	[1]	1,233,152,000	[1]
Impaired financing receivable, unpaid principal balance	2,969,496,000		1,430,588,000
Impaired financing receivable, related specific reserves	205,606,000		225,796,000
Impaired financing receivables, average recorded investment	2,198,076,000		1,233,152,000
Commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, recorded investment	425,330,000	[1]	479,343,000	[1]
Impaired financing receivable, unpaid principal balance	313,350,000		602,093,000
Impaired financing receivable, related specific reserves	75,973,000		90,594,000
Impaired financing receivables, average recorded investment	452,344,000		479,343,000
Corporate banking [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	51,940,000	[1]	43,485,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	42,186,000	[1]	53,762,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	39,271,000		30,131,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	35,100,000		52,100,000
Impaired financing receivable, related specific reserves	16,424,000		10,298,000
Impaired financing receivable with no related allowance recorded, average recorded investment	47,713,000		43,485,000
Impaired financing receivable with related allowance recorded, average recorded investment	47,974,000		53,762,000
Middle market commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	110,774,000	[1]	101,137,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	77,000,000	[1]	118,845,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	58,764,000		128,874,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	55,541,000		185,649,000
Impaired financing receivable, related specific reserves	17,012,000		26,130,000
Impaired financing receivable with no related allowance recorded, average recorded investment	105,956,000		101,137,000
Impaired financing receivable with related allowance recorded, average recorded investment	97,923,000		118,845,000
Santander real estate capital [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	3,818,000	[1]	751,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	1,840,000	[1]	9,382,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	3,818,000		751,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	594,000		8,136,000
Impaired financing receivable, related specific reserves	161,000		1,701,000
Impaired financing receivable with no related allowance recorded, average recorded investment	2,285,000		751,000
Impaired financing receivable with related allowance recorded, average recorded investment	5,611,000		9,382,000
Commercial and industrial loans [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	4,988,000	[1]	13,131,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	100,027,000	[1]	100,224,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	4,988,000		42,512,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	84,044,000		118,276,000
Impaired financing receivable, related specific reserves	39,503,000		50,252,000
Impaired financing receivable with no related allowance recorded, average recorded investment	9,060,000		13,131,000
Impaired financing receivable with related allowance recorded, average recorded investment	100,126,000		100,224,000
Multi-family loans [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	25,262,000	[1]	27,031,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	5,857,000	[1]	11,418,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	25,262,000		27,031,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	4,724,000		8,456,000
Impaired financing receivable, related specific reserves	1,442,000		2,201,000
Impaired financing receivable with no related allowance recorded, average recorded investment	26,147,000		27,031,000
Impaired financing receivable with related allowance recorded, average recorded investment	8,638,000		11,418,000
Other commercial [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	154,000	[1]	0	[1]
Impaired financing receivable with related allowance recorded, recorded investment	1,484,000	[1]	177,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	154,000		0
Impaired financing receivable with related allowance recorded, unpaid principal balance	1,090,000		177,000
Impaired financing receivable, related specific reserves	1,431,000		12,000
Impaired financing receivable with no related allowance recorded, average recorded investment	77,000		0
Impaired financing receivable with related allowance recorded, average recorded investment	831,000		177,000
Consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable, recorded investment	2,737,645,000	[1]	753,809,000	[1]
Impaired financing receivable, unpaid principal balance	2,656,146,000		828,495,000
Impaired financing receivable, related specific reserves	129,633,000		135,202,000
Impaired financing receivables, average recorded investment	1,745,732,000		753,809,000
Residential mortgages [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	84,622,000	[1]	92,143,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	553,442,000	[1]	547,329,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	84,622,000		92,143,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	495,440,000		603,866,000
Impaired financing receivable, related specific reserves	120,211,000		124,746,000
Impaired financing receivable with no related allowance recorded, average recorded investment	88,383,000		92,143,000
Impaired financing receivable with related allowance recorded, average recorded investment	550,386,000		547,329,000
Home equity loans and lines of credit [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	29,334,000	[1]	31,074,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	58,165,000	[1]	54,900,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	29,334,000		31,074,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	49,340,000		63,975,000
Impaired financing receivable, related specific reserves	4,880,000		5,479,000
Impaired financing receivable with no related allowance recorded, average recorded investment	30,204,000		31,074,000
Impaired financing receivable with related allowance recorded, average recorded investment	56,533,000		54,900,000
Retail installment contracts and auto loans [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	38,769,000	[1]	0	[1]
Impaired financing receivable with related allowance recorded, recorded investment	1,933,382,000	[1]	0	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	38,626,000		0
Impaired financing receivable with related allowance recorded, unpaid principal balance	1,925,380,000		0
Impaired financing receivable, related specific reserves	942,000		0
Impaired financing receivable with no related allowance recorded, average recorded investment	19,385,000		0
Impaired financing receivable with related allowance recorded, average recorded investment	966,691,000		0
Personal unsecured loan [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	13,610,000	[1]	0	[1]
Impaired financing receivable with related allowance recorded, recorded investment	2,208,000	[1]	2,535,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	13,610,000		0
Impaired financing receivable with related allowance recorded, unpaid principal balance	2,208,000		2,535,000
Impaired financing receivable, related specific reserves	527,000		677,000
Impaired financing receivable with no related allowance recorded, average recorded investment	6,805,000		0
Impaired financing receivable with related allowance recorded, average recorded investment	2,372,000		2,535,000
Other consumer [Member]
Financing Receivable, Impaired [Line Items]
Impaired financing receivable with no related allowance recorded, recorded investment	7,130,000	[1]	8,345,000	[1]
Impaired financing receivable with related allowance recorded, recorded investment	16,983,000	[1]	17,483,000	[1]
Impaired financing receivable with no related allowance recorded, unpaid principal balance	7,130,000		17,420,000
Impaired financing receivable with related allowance recorded, unpaid principal balance	10,456,000		17,482,000
Impaired financing receivable, related specific reserves	3,073,000		4,300,000
Impaired financing receivable with no related allowance recorded, average recorded investment	7,738,000		8,345,000
Impaired financing receivable with related allowance recorded, average recorded investment	$ 17,233,000		$ 17,483,000

[1] Recorded investment includes deferred loan fees, net of deferred origination costs and unamortized purchase premiums, net of discounts as well as purchase accounting adjustments.