Document and Entity Information (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Entity Registrant Name	TRUSTCO BANK CORP N Y
Entity Central Index Key	0000357301
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float		$ 358,782,038
Entity Common Stock, Shares Outstanding	93,674,359
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q1
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2012