BUSINESS COMBINATIONS - fair value of the assets purchased, including goodwill, and liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Apr. 07, 2017	Dec. 31, 2016	Jun. 03, 2016	Mar. 11, 2016
Assets:
Loans, net				$ 314,000
Goodwill	$ 101,747		$ 64,649
Liabilities:
Deposits				63,000
Measurement Period Adjustments [Member]
Assets:
Total assets acquired				0
Liabilities:
Total liabilities assumed				0	$ 0
Scenario, Previously Reported [Member]
Assets:
Total assets acquired				314,300
Liabilities:
Total liabilities assumed				314,300
Restatement Adjustment [Member]
Assets:
Total assets acquired				314,300	417,444
Liabilities:
Total liabilities assumed				314,300	339,833
Bank shares, Inc [Member] | Measurement Period Adjustments [Member]
Assets:
Cash					0
Investment securities					95
Loans, net					(2,112)
Fixed assets					(628)
Core deposit intangibles					0
Goodwill					1,647
Other assets					998
Total assets acquired					0
Liabilities:
Deposits					0
Other liabilities					0
Bank shares, Inc [Member] | Scenario, Previously Reported [Member]
Assets:
Cash					28,243
Investment securities					66,912
Loans, net					268,249
Fixed assets					7,801
Core deposit intangibles					3,375
Goodwill					29,985
Other assets					12,879
Total assets acquired					417,444
Liabilities:
Deposits					337,341
Other liabilities					2,492
Total liabilities assumed					339,833
Bank shares, Inc [Member] | Restatement Adjustment [Member]
Assets:
Cash					28,243
Investment securities					67,007
Loans, net					266,137
Fixed assets					7,173
Core deposit intangibles					3,375
Goodwill					31,632
Other assets					13,877
Liabilities:
Deposits					337,341
Other liabilities					$ 2,492
BMO Harris Bank [Member] | Measurement Period Adjustments [Member]
Assets:
Cash				0
Loans, net				0
Fixed assets				0
Core deposit intangibles				(135)
Goodwill				163
Other assets				(28)
Liabilities:
Deposits				0
Other liabilities				0
BMO Harris Bank [Member] | Scenario, Previously Reported [Member]
Assets:
Cash				234,094
Loans, net				62,671
Fixed assets				3,715
Core deposit intangibles				5,223
Goodwill				7,645
Other assets				952
Liabilities:
Deposits				314,248
Other liabilities				52
BMO Harris Bank [Member] | Restatement Adjustment [Member]
Assets:
Cash				234,094
Loans, net				62,671
Fixed assets				3,715
Core deposit intangibles				5,088
Goodwill				7,808
Other assets				924
Liabilities:
Deposits				314,248
Other liabilities				$ 52
Gulf Shore Banc shares Inc [Member] | Measurement Period Adjustments [Member]
Assets:
Cash		$ 0
Investment securities		0
Loans, net		(8)
Fixed assets		0
Other real estate owned		0
Core deposit intangibles		0
Goodwill		8
Other assets		0
Total assets acquired		0
Liabilities:
Deposits		0
Other liabilities		0
Total liabilities assumed		0
Gulf Shore Banc shares Inc [Member] | Scenario, Previously Reported [Member]
Assets:
Cash		55,540
Investment securities		316
Loans, net		250,884
Fixed assets		1,307
Other real estate owned		13
Core deposit intangibles		3,927
Goodwill		37,090
Other assets		8,572
Total assets acquired		357,649
Liabilities:
Deposits		285,350
Other liabilities		1,382
Total liabilities assumed		286,732
Gulf Shore Banc shares Inc [Member] | Restatement Adjustment [Member]
Assets:
Cash		55,540
Investment securities		316
Loans, net		250,876
Fixed assets		1,307
Other real estate owned		13
Core deposit intangibles		3,927
Goodwill		37,098
Other assets		8,572
Total assets acquired		357,649
Liabilities:
Deposits		285,350
Other liabilities		1,382
Total liabilities assumed		$ 286,732