BUSINESS SEGMENTS (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information
Interest income	$ 302,127	$ 280,317	$ 278,865	$ 276,172	$ 270,477	$ 264,632	$ 255,445	$ 263,261	$ 1,137,481	$ 1,053,815	$ 1,153,698
Charge for funds used									(360,465)	(317,143)	(283,384)
Interest spread on funds used									777,016	736,672	870,314
Interest expense	(29,425)	(26,169)	(25,281)	(23,968)	(23,536)	(24,343)	(27,953)	(27,544)	(104,843)	(103,376)	(112,820)
Credit on funds provided									360,465	317,143	283,384
Interest spread on funds provided									255,622	213,767	170,564
Net interest income before provision for credit losses	272,702	254,148	253,584	252,204	246,941	240,289	227,492	235,717	1,032,638	950,439	1,040,878
(Reversal of) provision for credit losses	10,461	9,525	6,053	1,440	(2,000)	7,736	3,494	4,987	27,479	14,217	49,158
Depreciation, amortization and (accretion), net									83,348	46,202	82,553
Segment income (loss) before income taxes	161,137	$ 123,464	$ 142,916	$ 144,671	148,485	$ 138,989	$ 144,421	$ 146,826	572,188	578,721	447,023
Goodwill	469,433				469,433				469,433	469,433	469,433
Segment assets	34,788,840				32,350,922				34,788,840	32,350,922	28,743,592
Retail Banking
Segment Reporting Information
Interest income									315,146	331,755	378,445
Charge for funds used									(95,970)	(86,769)	(94,162)
Interest spread on funds used									219,176	244,986	284,283
Interest expense									(60,180)	(53,088)	(48,020)
Credit on funds provided									300,446	261,117	225,873
Interest spread on funds provided									240,266	208,029	177,853
Net interest income before provision for credit losses									459,442	453,015	462,136
(Reversal of) provision for credit losses									(4,356)	(5,835)	14,979
Depreciation, amortization and (accretion), net									601	10,051	14,376
Segment income (loss) before income taxes									170,129	212,036	181,286
Goodwill	357,207				357,207				357,207	357,207	357,207
Segment assets	7,821,610				7,095,737				7,821,610	7,095,737	7,621,808
Commercial Banking
Segment Reporting Information
Interest income									726,013	654,966	715,075
Charge for funds used									(216,849)	(163,601)	(141,652)
Interest spread on funds used									509,164	491,365	573,423
Interest expense									(16,892)	(18,025)	(15,650)
Credit on funds provided									38,636	36,251	38,592
Interest spread on funds provided									21,744	18,226	22,942
Net interest income before provision for credit losses									530,908	509,591	596,365
(Reversal of) provision for credit losses									31,835	20,052	34,179
Depreciation, amortization and (accretion), net									(35,534)	(28,096)	(8,372)
Segment income (loss) before income taxes									377,913	382,233	293,425
Goodwill	112,226				112,226				112,226	112,226	112,226
Segment assets	19,128,510				17,923,319				19,128,510	17,923,319	15,595,862
Other
Segment Reporting Information
Interest income									96,322	67,094	60,178
Charge for funds used									(47,646)	(66,773)	(47,570)
Interest spread on funds used									48,676	321	12,608
Interest expense									(27,771)	(32,263)	(49,150)
Credit on funds provided									21,383	19,775	18,919
Interest spread on funds provided									(6,388)	(12,488)	(30,231)
Net interest income before provision for credit losses									42,288	(12,167)	(17,623)
(Reversal of) provision for credit losses									0	0	0
Depreciation, amortization and (accretion), net									118,281	64,247	76,549
Segment income (loss) before income taxes									24,146	(15,548)	(27,688)
Goodwill	0				0				0	0	0
Segment assets	$ 7,838,720				$ 7,331,866				$ 7,838,720	$ 7,331,866	$ 5,525,922