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The fair value discount of the available for sale securities at date of acquisition.

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The outstanding shares of the acquiree in a business acquisition.

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The fair value premium of the time deposits at the date of acquisition.

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Net amount of the investment in a contractual right to receive money on demand or on fixed or determinable dates that is recognized as an asset in the creditor's statement of financial position. Examples include, but are not limited to, credit card receivables, notes receivable and receivables relating to lessor's rights to payments from leases other than operating leases that have been recorded as assets. Excludes trade accounts receivable with contractual maturity of one year or less and arose from the sale of goods or services.

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Nature of Operations and Summary of Significant Accounting Policies - Recent Acquisitions (Details) - USD ($)				12 Months Ended
	Oct. 01, 2018	Jan. 02, 2018	Aug. 15, 2017	Dec. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquisitions
Goodwill				$ 15,845,000	$ 17,477,000		$ 3,902,000	$ 523,000
Total assets				6,371,928,000	3,884,163,000		3,393,133,000
Fair Value of available for sale securities				290,243,000	331,071,000
Time deposits at fair value				$ 2,174,339,000	$ 680,454,000
Core Deposits
Acquisitions
Useful life				10 years
Customer Lists
Acquisitions
Useful life					21 months
MCS
Acquisitions
Percentage of voting interests acquired			100.00%
Purchase price paid shares			$ 8,100,000
Goodwill			3,800,000
Intangible assets			$ 1,600,000
FMBI \| Stock Purchase Agreement
Acquisitions
Total cost		$ 5,500,000
Goodwill		988,000
Intangible assets		478,000
Time deposits		16,700,000
Time deposits at fair value		16,900,000
Fair value premium of acquired time deposits		$ 185,000
Time deposits, fair value premium, accretion period		20 months
Acquired loan portfolio		$ 27,900,000
Acquired loan portfolio at fair value		27,500,000
Fair value discount on acquired loan portfolio		$ 458,000
Acquired loan portfolio, fair value discount, accretion period		39 months
FMBI \| Core Deposits
Acquisitions
Useful life				10 years
FMBI \| Core Deposits \| Stock Purchase Agreement
Acquisitions
Useful life		10 years
FM Bancorp, Inc
Acquisitions
Outstanding shares of the acquiree	27,537
Share price per share	$ 795.29
Total cost	$ 21,900,000
Goodwill	6,900,000
Intangible assets	1,900,000
Fair Value of available for sale securities	66,300,000
Fair value discount on available for sale securities	1,000,000
Time deposits	95,700,000
Time deposits at fair value	95,700,000
Acquired loan portfolio	35,400,000
Acquired loan portfolio at fair value	34,800,000
Fair value discount on acquired loan portfolio	625,000
Discount related to interest assumption	279,000
Discount related to credit assumption	$ 346,000
Acquired loan portfolio, fair value discount, accretion period	72 months
FM Bancorp, Inc \| Core Deposits
Acquisitions
Useful life	10 years
NattyMac, LLC
Acquisitions
Goodwill					$ 3,700,000
Intangible assets					1,600,000
Repayments of subordinated debt					$ 30,000,000
NattyMac, LLC \| Customer Lists
Acquisitions
Useful life				21 months	21 months
FMBI
Acquisitions
Total assets							$ 43,000,000
FM Bancorp
Acquisitions
Total assets						$ 110,000,000
Fair Value of available for sale securities						66,300,000
Time deposits						95,700,000
Net loans receivable						$ 35,000,000