Employee Benefits - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2013
Employee Benefits [Abstract]
Age of employees under condition one	55 years
Age of employees under condition two	50 years
Period of service under condition one	5 years
Period of service under condition two	15 years
Minimum period of service at the time of termination hired before 2001	15 years
Condition under retiree healthcare plan	We sponsor a retiree healthcare plan in which all employees age 55 with five years of service (or employees age 50 with 15 years of service who are terminated under conditions that entitle them to a severance benefit) are eligible to participate
Death benefit plan description	Death benefit plan that provided a death benefit for a very limited number of (i) former Key employees who retired from their employment with Key prior to 1994; (ii) former Key employees who elect a grandfathered pension benefit under the KeyCorp Cash Balance Pension Plan; and (iii) Key employees who otherwise were provided a historical death benefit at the time of their termination