Business Combination - Unaudited Pro Forma (Details) - MB Financial, Inc. - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2019	Sep. 30, 2019
Business Acquisition [Line Items]
Unaudited pro forma net income available to common shareholders	$ 520	$ 1,840
Net Interest Income
Business Acquisition [Line Items]
Unaudited pro forma revenue	1,223	3,696
Non Interest Income
Business Acquisition [Line Items]
Unaudited pro forma revenue	$ 739	$ 2,601

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(3)
-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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