Business Combinations and Asset Acquisitions	12 Months Ended
Business Combinations and Asset Acquisitions	Dec. 31, 2019
Business Combinations And Asset Acquisitions [Abstract]
Business Combinations and Asset Acquisitions	Business Combinations and Asset Acquisitions Bank Acquisitions On November 1, 2019, the Company completed its acquisition of SBC. SBC was the parent company of Countryside Bank. Through this business combination, the Company acquired Countryside Bank's six banking offices located in Countryside, Burbank, Darien, Homer Glen, Oak Brook and Chicago, Illinois. As of the acquisition date, the Company acquired approximately $619.8 million in assets, including approximately $423.0 million in loans, and approximately $507.8 million in deposits. The Company recorded goodwill of approximately $40.3 million related to the acquisition. On October 7, 2019, the Company completed its acquisition of STC. STC was the parent company of STC Capital Bank. Through this business combination, the Company acquired STC Capital Bank's five banking offices located in the communities of St. Charles, Geneva and South Elgin, Illinois. As of the acquisition date, the Company acquired approximately $250.1 million in assets, including approximately $174.3 million in loans, and approximately $201.2 million in deposits. The Company recorded goodwill of approximately $19.1 million related to the acquisition. On May 24, 2019, the Company completed its acquisition of ROC. ROC was the parent company of Oak Bank. Through this business combination, the Company acquired Oak Bank's one banking location in Chicago, Illinois. As of the acquisition date, the Company acquired approximately $223.4 million in assets, including approximately $124.7 million in loans, and approximately $161.2 million in deposits. The Company recorded goodwill of approximately $11.7 million related to the acquisition. On December 7, 2018, the Company completed its acquisition of certain assets and the assumption of certain liabilities of AEB. Through this asset acquisition, the Company acquired approximately $164.0 million in assets, including approximately $119.3 million in loans, and approximately $150.8 million in deposits. On August 1, 2018, the Company completed its acquisition of CSC. CSC was the parent company of Delaware Place Bank. Through this business combination, the Company acquired Delaware Place Bank's one banking location in Chicago, Illinois. As of the acquisition date, the Company acquired approximately $282.8 million in assets, including approximately $152.7 million in loans, and approximately $213.1 million in deposits. Additionally, the Company recorded goodwill of approximately $26.6 million related to the acquisition. Wealth Management Acquisitions On December 14, 2018, the Company acquired Elektra, the parent company of CDEC. CDEC is a provider of Qualified Intermediary services (as defined by U.S. Treasury regulations) for taxpayers seeking to structure tax-deferred like-kind exchanges under Internal Revenue Code Section 1031. CDEC has successfully facilitated more than 8,000 like-kind exchanges in the past decade for taxpayers nationwide. These transactions typically generate customer deposits during the period following the sale of the property until such proceeds are used to purchase a replacement property. The Company recorded goodwill of approximately $37.3 million related to the acquisition. Mortgage Banking Acquisitions On January 4, 2018, the Company acquired Veterans First with assets including mortgage-servicing-rights on approximately 10,000 loans, totaling an estimated $1.6 billion in unpaid principal balance. The Company recorded goodwill of approximately $9.1 million related to the acquisition. On February 14, 2017, the Company acquired certain assets and assumed certain liabilities of the mortgage banking business of AHM. The Company recorded goodwill of approximately $1.0 million related to the acquisition. PCI loans Purchased loans acquired in a business combination are recorded at estimated fair value on their purchase date. For PCI loans, expected future cash flows at the purchase date in excess of the fair value of loans are recorded as interest income over the life of the loans if the timing and amount of the future cash flows is reasonably estimable (“accretable yield”). The difference between contractually required payments and the cash flows expected to be collected at acquisition is referred to as the non-accretable difference and represents probable losses in the portfolio. In determining the acquisition date fair value of PCI loans, and in subsequent accounting, the Company aggregates these purchased loans into pools of loans by common risk characteristics, such as credit risk rating and loan type. Subsequent to the purchase date, increases in cash flows over those expected at the purchase date are recognized as interest income prospectively. Subsequent decreases to the expected cash flows will result in a provision for loan losses. The Company purchased a portfolio of life insurance premium finance receivables in 2009. These purchased life insurance premium finance receivables are valued on an individual basis. If credit related conditions deteriorate, an allowance related to these loans will be established as part of the provision for credit losses. See Note 4, “Loans,” for more information on loans acquired with evidence of credit quality deterioration since origination.