SEGMENT REPORTING (Details) - USD ($) $ in Thousands			3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Net interest revenue			$ 117,478	$ 112,316	$ 232,089	$ 223,475
Provision for credit losses			1,000	2,000	2,000	3,000
Net interest revenue, after provision for credit losses			116,478	110,316	230,089	220,475
Noninterest revenue			68,130	68,526	138,999	133,253
Noninterest expense			127,553	127,561	254,662	269,073
Income before income taxes			57,055	51,281	114,426	84,655
Income tax expense (benefit)			19,166	16,589	38,444	27,414
Net income			37,889	34,692	75,982	57,241
Total assets at end of period	$ 14,843,130	$ 14,137,160	14,843,130	14,137,160	14,843,130	14,137,160	$ 14,724,388
Depreciation and amortization	15,048	14,355	7,533	7,169
Banking Services Group [Member]
Net interest revenue			113,117	109,851	224,169	218,751
Net interest revenue, after provision for credit losses			113,117	109,851	224,169	218,751
Noninterest revenue			21,681	23,309	43,558	46,015
Noninterest expense			75,627	76,000	150,476	152,905
Income before income taxes			59,171	57,160	117,251	111,861
Income tax expense (benefit)			20,926	19,386	40,558	38,330
Net income			38,245	37,774	76,693	73,531
Total assets at end of period	11,462,105	10,865,604	11,462,105	10,865,604	11,462,105	10,865,604
Depreciation and amortization	11,053	10,643	5,550	5,329
Mortgage [Member]
Net interest revenue			4,322	2,820	7,852	5,431
Net interest revenue, after provision for credit losses			4,322	2,820	7,852	5,431
Noninterest revenue			6,134	7,868	15,126	9,698
Noninterest expense			6,917	6,583	13,779	12,446
Income before income taxes			3,539	4,105	9,199	2,683
Income tax expense (benefit)			1,320	1,531	3,420	973
Net income			2,219	2,574	5,779	1,710
Total assets at end of period	639,130	489,754	639,130	489,754	639,130	489,754
Depreciation and amortization	305	291	153	146
Insurance Agencies [Member]
Net interest revenue			11	16	21	35
Net interest revenue, after provision for credit losses			11	16	21	35
Noninterest revenue			31,286	28,543	64,399	61,908
Noninterest expense			26,676	24,781	52,650	50,263
Income before income taxes			4,621	3,778	11,770	11,680
Income tax expense (benefit)			1,846	1,511	4,690	4,651
Net income			2,775	2,267	7,080	7,029
Total assets at end of period	228,507	219,280	228,507	219,280	228,507	219,280
Depreciation and amortization	2,368	2,094	1,180	1,034
Wealth Management [Member]
Net interest revenue			8	2	13	2
Net interest revenue, after provision for credit losses			8	2	13	2
Noninterest revenue			5,759	5,766	11,375	11,301
Noninterest expense			4,181	4,397	8,129	8,496
Income before income taxes			1,586	1,371	3,259	2,807
Income tax expense (benefit)			591	511	1,212	1,018
Net income			995	860	2,047	1,789
Total assets at end of period	22,475	23,120	22,475	23,120	22,475	23,120
Depreciation and amortization	51	57	25	29
General Corporate And Other [Member]
Net interest revenue			20	(373)	34	(744)
Provision for credit losses			1,000	2,000	2,000	3,000
Net interest revenue, after provision for credit losses			(980)	(2,373)	(1,966)	(3,744)
Noninterest revenue			3,270	3,040	4,541	4,331
Noninterest expense			14,152	15,800	29,628	44,963
Income before income taxes			(11,862)	(15,133)	(27,053)	(44,376)
Income tax expense (benefit)			(5,517)	(6,350)	(11,436)	(17,558)
Net income			(6,345)	(8,783)	(15,617)	(26,818)
Total assets at end of period	2,490,913	2,539,402	2,490,913	2,539,402	$ 2,490,913	$ 2,539,402
Depreciation and amortization	$ 1,271	$ 1,270	$ 625	$ 631