Derivatives and Hedging Activities - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Credit Derivatives [Line Items]
Derivative assets after effects of bilateral collateral and master netting agreements	$ 160
Derivative liabilities after effects of bilateral collateral and master netting agreements	91
Derivative assets not designated as hedging instruments after effects of bilateral collateral and master netting agreements, and a reserve for potential future losses	533
Derivative liabilities not designated as hedging instruments after effects of bilateral collateral and master netting agreements, and a reserve for potential future losses	675
Amount of debt being hedged under foreign currency exchange risk	0
Reclassify of net losses on derivative instruments from AOCI	30
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	16 years
Other Comprehensive income unrealized loss on derivatives arising during period net of tax	9
Cash collateral netted against derivative assets	494	486
Collateral netted against derivative liabilities	27	11
Gross exposure on derivatives, after taking into account the effects of bilateral collateral and master netting agreements	890
Net exposure on derivatives, after taking into account, the effects of bilateral collateral and master netting agreements	193
Net exposure on derivatives to broker-dealers and banks, after the application of master netting agreements and collateral	9
Additional collateral held in the form of securities	184
Default reserve associated with uncollateralized contracts	19	22
Gross exposure on derivatives after taking into account effects of master netting agreements	554
Net exposure on derivatives with clients after application of master netting agreements collateral and related reserve	500
Net liability position totaled	191	250
Cash and securities collateral posted	66	64
KeyBank [Member]
Credit Derivatives [Line Items]
Net liability position totaled	494
Derivative assets included in net liability position	500
Derivative liabilities included in net liability position	994,000
Cash and securities collateral posted	489
Payments to terminate contracts	13
Key Corp [Member]
Credit Derivatives [Line Items]
Net liability position totaled	26
Derivative liabilities included in net liability position	26
Cash and securities collateral posted	24
Additional collateral amount	3
Payments to terminate contracts	$ 3