Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Deferred Compensation

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Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Loans

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Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Tax Adjustment on Previous Fair Value Measurement

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Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Unfunded Commitments

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Compensation

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Tax Adjustment on Previously Stated Fair Value Measurement

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Unfunded Commitments

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Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

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-Name Accounting Standards Codification
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Fair value at acquisition-date of the assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interests issued by the acquirer, including but not limited to, instruments or interests issued or issuable in consideration for the business combination.

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Amount of assets acquired at the acquisition date.

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Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investments in debt and equity securities, including, but not limited to, held-to-maturity, trading and available-for-sale expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount due from customers or clients for goods or services, including trade receivables, that have been delivered or sold in the normal course of business, and amounts due from others, including related parties expected to be converted to cash, sold or exchanged within one year or the normal operating cycle, if longer, acquired at the acquisition date.

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Amount of liabilities incurred for goods and services received that are used in an entity's business and related party payables, assumed at the acquisition date.

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The amount of financial assets (as defined) recognized as of the acquisition date.

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Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

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Amount of liabilities assumed at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Fair value at acquisition-date of the equity interest in the acquiree held by the acquirer, immediately before the acquisition date for businesses combined in stages.

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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Business Combination - Schedule of Purchase Price Calculation and Identifiable Assets Purchased and Liabilities Assumed (Details) - USD ($) $ in Millions		6 Months Ended	9 Months Ended	12 Months Ended
	Aug. 01, 2016	Jun. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
LIABILITIES
Goodwill				$ 1,386
First Niagara Bank, N.A. [Member]
Consideration paid:
KeyCorp common stock issued	$ 2,831
Cash payments to First Niagara stockholders	811
Exchange of First Niagara preferred stock for KeyCorp preferred stock	350
Total consideration paid	3,992
ASSETS
Cash and due from banks and short-term investments	620
Investment securities	9,012
Other investments	297
Loans	23,590	$ 23,590
Premises and equipment	245
Other intangible assets	385
Accrued income and other assets	1,467
Total assets	35,616
LIABILITIES
Deposits	28,994
Bank notes and other short-term borrowings	2,698
Accrued expense and other liabilities	490
Long-term debt	846
Total liabilities	33,028
Net identifiable assets acquired	2,588
Goodwill	$ 1,404
Increase (decrease) in in fair value of loans acquired		(55)
Tax adjustment on previous fair value measurement		1,467
Increase (decrease) in tax adjustment on previous fair value measurement		18
Unfunded lending-related commitments		65
Increase (decrease) in unfunded lending-related commitments		(2)
Deferred compensation		41
Increase (decrease) deferred compensation		2
Scenario, Previously Reported [Member] \| First Niagara Bank, N.A. [Member]
ASSETS
Loans		23,645
LIABILITIES
Tax adjustment on previous fair value measurement		1,449
Unfunded lending-related commitments		67
Deferred compensation		$ 39
Interest Income [Member] \| First Niagara Bank, N.A. [Member]
LIABILITIES
Increase (decrease) in in fair value of loans acquired			$ 42
Provision for Credit Losses [Member] \| First Niagara Bank, N.A. [Member]
LIABILITIES
Increase (decrease) in in fair value of loans acquired			1
Other Noninterest Income [Member] \| First Niagara Bank, N.A. [Member]
LIABILITIES
Increase (decrease) in in fair value of loans acquired			(3)
Increase (decrease) in unfunded lending-related commitments			$ (4)