ACQUISITIONS - Estimated FV of Assets Acquired & Liab Assumed(Details) - USD ($) $ in Thousands	Sep. 30, 2017	May 12, 2017	Dec. 31, 2016
Assets
Goodwill	$ 231,806		$ 221,526
Island Bancorp, Inc. [Member]
Assets
Cash		$ 11,137
Loans		155,551
Premises and equipment		5,828
Goodwill		10,280
Core deposit intangible		2,964
Other assets		4,629
Total assets acquired		190,389
Liabilities
Deposits		159,580
Borrowings		2,475
Other liabilities		18
Total liabilities assumed		162,073
Purchase price		$ 28,316