SEGMENT REPORTING (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Net interest revenue	$ 114,611	$ 111,159
Provision for credit losses	1,000	1,000	$ 4,000
Net interest revenue, after provision for credit losses	113,611	110,159
Noninterest revenue	70,869	64,727
Noninterest expense	127,109	141,512
Income before income taxes	57,371	33,374
Income tax expense (benefit)	19,278	10,825
Net income	38,093	22,549
Total assets at end of period	14,866,054	13,926,398	$ 14,724,388
Depreciation and amortization	7,515	7,187
Banking Services Group [Member]
Net interest revenue	111,053	108,901
Net interest revenue, after provision for credit losses	111,053	108,901
Noninterest revenue	21,877	22,706
Noninterest expense	75,850	76,906
Income before income taxes	57,080	54,701
Income tax expense (benefit)	19,633	17,629
Net income	37,447	37,072
Total assets at end of period	11,566,533	10,749,801
Depreciation and amortization	5,502	5,314
Mortgage [Member]
Net interest revenue	3,530	2,610
Net interest revenue, after provision for credit losses	3,530	2,610
Noninterest revenue	8,990	1,830
Noninterest expense	6,862	5,863
Income before income taxes	5,658	(1,423)
Income tax expense (benefit)	2,098	(502)
Net income	3,560	(921)
Total assets at end of period	543,022	399,532
Depreciation and amortization	152	145
Insurance Agencies [Member]
Net interest revenue	11	19
Net interest revenue, after provision for credit losses	11	19
Noninterest revenue	33,113	33,364
Noninterest expense	25,974	25,482
Income before income taxes	7,150	7,901
Income tax expense (benefit)	2,844	3,140
Net income	4,306	4,761
Total assets at end of period	216,784	210,535
Depreciation and amortization	1,187	1,060
Wealth Management [Member]
Net interest revenue	5	1
Net interest revenue, after provision for credit losses	5	1
Noninterest revenue	5,617	5,535
Noninterest expense	3,948	4,099
Income before income taxes	1,674	1,437
Income tax expense (benefit)	620	506
Net income	1,054	931
Total assets at end of period	21,373	15,370
Depreciation and amortization	26	28
General Corporate And Other [Member]
Net interest revenue	12	(372)
Provision for credit losses	1,000	1,000
Net interest revenue, after provision for credit losses	(988)	(1,372)
Noninterest revenue	1,272	1,292
Noninterest expense	14,475	29,162
Income before income taxes	(14,191)	(29,242)
Income tax expense (benefit)	(5,917)	(9,948)
Net income	(8,274)	(19,294)
Total assets at end of period	2,518,342	2,551,160
Depreciation and amortization	$ 648	$ 640