Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Interest and dividend income:
Interest and fees on loans	$ 38,091	$ 36,044
Interest and dividends on securities available for sale:
U. S. government sponsored enterprises	750	595
State and political subdivisions	7	12
Mortgage-backed securities and collateralized mortgage obligations-residential	1,763	1,958
Corporate bonds	133	151
Small Business Administration-guaranteed participation securities	352	415
Mortgage-backed securities and collateralized mortgage obligations-commercial	42	23
Other securities	5	4
Total interest and dividends on securities available for sale	3,052	3,158
Interest on held to maturity securities:
Mortgage-backed securities and collateralized mortgage obligations-residential	260	316
Corporate bonds	0	154
Total interest on held to maturity securities	260	470
Federal Reserve Bank and Federal Home Loan Bank stock	77	134
Interest on federal funds sold and other short-term investments	2,017	1,246
Total interest income	43,497	41,052
Interest on deposits:
Interest-bearing checking	106	124
Savings	419	430
Money market deposit accounts	439	466
Time deposits	2,860	2,283
Interest on short-term borrowings	358	349
Total interest expense	4,182	3,652
Net interest income	39,315	37,400
Provision for loan losses	300	600
Net interest income after provision for loan losses	39,015	36,800
Noninterest income:
Other	219	232
Total noninterest income	4,679	4,727
Noninterest expenses:
Salaries and employee benefits	10,422	10,210
Net occupancy expense	4,315	4,109
Equipment expense	1,751	1,556
Professional services	1,430	1,928
Outsourced services	1,925	1,500
Advertising expense	630	713
FDIC and other insurance	1,023	1,047
Other real estate expense, net	372	499
Other	2,287	2,457
Total noninterest expenses	24,155	24,019
Income before taxes	19,539	17,508
Income taxes	4,731	6,561
Net income	$ 14,808	$ 10,947
Net income per share:
Basic (in dollars per share)	$ 0.154	$ 0.114
Diluted (in dollars per share)	$ 0.153	$ 0.114
Trustco Financial Services Income [Member]
Noninterest income:
Non-interest income	$ 1,815	$ 1,858
Fees for Services to Customers [Member]
Noninterest income:
Non-interest income	$ 2,645	$ 2,637