Consolidated Statements of Income (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Interest and dividend income:
Interest and fees on loans	$ 32,425	$ 31,677
Interest and dividends on securities available for sale:
Total interest and dividends on securities available for sale	4,724	5,791
Interest on held to maturity securities:
Total interest on held to maturity securities	1,824	1,903
Interest on federal funds sold and other short-term investments	320	246
Total interest income	39,293	39,617
Interest expense:
Interest-bearing checking	78	65
Savings	1,102	933
Money market deposit accounts	923	1,227
Time deposits	3,418	4,443
Interest on short-term borrowings	388	407
Total interest expense	5,909	7,075
Net interest income	33,384	32,542
Provision for loan losses	3,100	4,600
Net interest income after provision for loan losses	30,284	27,942
Noninterest income:
Trustco Financial Services income	1,394	1,574
Fees for services to customers	2,240	2,094
Net gain on securities transactions	677	287
Other	207	316
Total noninterest income	4,518	4,271
Noninterest expense:
Salaries and employee benefits	7,743	7,026
Net occupancy expense	3,795	3,737
Equipment expense	1,520	1,332
Professional services	1,436	1,485
Outsourced services	1,250	1,350
Advertising expense	809	706
FDIC and other insurance expense	880	1,851
Other real estate expense, net	966	1,590
Other	2,245	1,769
Total noninterest expense	20,644	20,846
Income before income taxes	14,158	11,367
Income taxes	5,249	3,985
Net income	8,909	7,382
Earnings per share:
Basic (in dollars per share)	$ 0.095	$ 0.096
Diluted (in dollars per share)	$ 0.095	$ 0.096
U. S. Government Sponsored Enterprises [Member]
Interest and dividends on securities available for sale:
Total interest and dividends on securities available for sale	2,304	3,199
Interest on held to maturity securities:
Total interest on held to maturity securities	25	0
State and Political Subdivisions [Member]
Interest and dividends on securities available for sale:
Total interest and dividends on securities available for sale	410	784
Mortgage-Backed Securities and Collateralized Mortgage Obligations-Residential [Member]
Interest and dividends on securities available for sale:
Total interest and dividends on securities available for sale	1,093	608
Interest on held to maturity securities:
Total interest on held to maturity securities	1,290	1,188
Corporate Bonds [Member]
Interest and dividends on securities available for sale:
Total interest and dividends on securities available for sale	822	1,139
Interest on held to maturity securities:
Total interest on held to maturity securities	509	715
Other Securities [Member]
Interest and dividends on securities available for sale:
Total interest and dividends on securities available for sale	$ 95	$ 61