Business Combination (Unaudited Pro Forma) (Detail) - MB Financial, Inc. - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Business Acquisition
Unaudited pro forma net income attributable to common shareholders	$ 891	$ 655
Net Interest Income
Business Acquisition
Unaudited pro forma revenue	1,242	1,181
Noninterest Income
Business Acquisition
Unaudited pro forma revenue	$ 1,205	$ 1,006

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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
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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
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-URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463

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-Publisher FASB
-Name Accounting Standards Codification
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