Derivatives and Hedging Activities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012
Credit Derivatives [Line Items]
Derivative assets after effects of bilateral collateral and master netting agreements	$ 115
Derivative assets not designated as hedging instruments after effects of bilateral collateral and master netting agreements, and a reserve for potential future losses	346
Derivative liabilities not designated as hedging instruments after effects of bilateral collateral and master netting agreements, and a reserve for potential future losses	456
Reclassify of net losses on derivative instruments from AOCI	26
Length of time hedge in cash flow hedge	12 months
Reclassification of net gains related to terminated cash flow hedges from AOCI to income	6
Maximum length of time over which forecasted transactions are hedged, years	15 years
Other Comprehensive income unrealized gain on derivatives arising during period net of tax	1
Cash collateral netted against derivative assets	368	494	513
Collateral netted against derivative liabilities	9	27	11
Maximum cash collateral not netted against gross exposure	1
Cash collateral not netted transferred with clearing organization	1
Gross exposure on derivatives, after taking into account the effects of bilateral collateral and master netting agreements	626
Net exposure on derivatives, after taking into account, the effects of bilateral collateral and master netting agreements	119
Net exposure on derivatives to broker-dealers and banks, after the application of master netting agreements and collateral	3
Additional collateral held in the form of securities	122
Default reserve associated with uncollateralized contracts	16	19
Gross exposure on derivatives after taking into account effects of master netting agreements	385
Net exposure on derivatives with clients after application of master netting agreements collateral and related reserve	342
Net liability position totaled	132	191	217
Cash and securities collateral posted	48	66	70
Maximum [Member]
Credit Derivatives [Line Items]
Derivative liabilities after effects of bilateral collateral and master netting agreements	1
KeyBank [Member]
Credit Derivatives [Line Items]
Net liability position totaled	332
Derivative assets included in net liability position	414
Derivative liabilities included in net liability position	746
Cash and securities collateral posted	334
Payments to terminate contracts	13
Key Corp [Member]
Credit Derivatives [Line Items]
Net liability position totaled	9
Derivative liabilities included in net liability position	9
Cash and securities collateral posted	7
Additional collateral amount	3	3	3
Payments to terminate contracts	$ 3