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The amount of identifiable intangible assets recognized as of the acquisition date.

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GOODWILL, CORE DEPOSIT PREMIUM AND OTHER INTANGIBLE ASSETS (Goodwill narrative) (Details) - USD ($)		6 Months Ended
	May 18, 2018	Jun. 30, 2020	Dec. 31, 2019	Nov. 30, 2019	May 10, 2019
Goodwill [Line Items]
Goodwill		$ 446,345,000	$ 446,345,000
Goodwill impairment		$ 0
Rockford Bank And Trust Company
Goodwill [Line Items]
Goodwill				$ 19,200,000
Rockford Bank And Trust Company \| Core Deposits
Goodwill [Line Items]
Intangibles recognized				$ 1,800,000
Intangibles, amortization period	10 years
Blue Valley Ban Corp.
Goodwill [Line Items]
Goodwill					$ 35,400,000
Blue Valley Ban Corp. \| Core Deposits
Goodwill [Line Items]
Intangibles recognized					$ 11,400,000
Intangibles, amortization period	10 years