Regulatory Capital Requirements (Details) $ in Thousands		Mar. 31, 2022 USD ($) Classification	Dec. 31, 2021 USD ($)
Trustco Bank [Member]
Compliance With Regulatory Capital Requirements Under Banking Regulations Information [Abstract]
Number of classifications for prompt corrective action regulations provide | Classification		5
Tier One Risk Based Capital [Abstract]
Tier 1 leverage capital		$ 575,895	$ 570,594
Common equity Tier 1 capital		575,895	570,594
Tier 1 risk-based capital		575,895	570,594
Total risk-based capital		$ 614,433	$ 608,308
Risk Based Ratios [Abstract]
Tier 1 leverage ratio, ratio		0.09286	0.09324
Common equity Tier 1 capital, ratio		0.18743	0.18954
Tier 1 risk-based capital, ratio		0.18743	0.18954
Total risk-based capital, ratio		0.19997	0.20206
Leverage Ratios [Abstract]
Tier 1 leverage ratio, well capitalized	[1]	0.05000	0.05000
Tier 1 leverage ratio, minimum for capital adequacy plus capital conservation	[1],[2]	0.04000	0.04000
Common equity Tier 1 capital, well capitalized	[1]	0.06500	0.06500
Common equity Tier 1 capital, minimum for capital adequacy plus capital conservation	[1],[2]	0.07000	0.07000
Tier 1 risk-based capital, well capitalized	[1]	0.08000	0.08000
Tier 1 risk-based capital, minimum for capital adequacy plus capital conservation	[1],[2]	0.08500	0.08500
Total risk-based capital, well capitalized	[1]	0.10000	0.10000
Total risk-based capital, minimum for capital adequacy plus capital conservation	[1],[2]	0.10500	0.10500
Common equity Tier 1 capital conservation buffer		0.0250	0.0250
Tier 1 risk based capital ratio, capital conservation buffer		0.0250	0.0250
Total risk based capital ratio, capital conservation buffer		0.0250	0.0250
TrustCo Bank Corp NY [Member]
Tier One Risk Based Capital [Abstract]
Tier 1 leverage capital		$ 594,711	$ 588,427
Common equity Tier 1 capital		594,711	588,427
Tier 1 risk-based capital		594,711	588,427
Total risk-based capital		$ 633,260	$ 626,150
Risk Based Ratios [Abstract]
Tier 1 leverage ratio, ratio		0.09585	0.09614
Common equity Tier 1 capital, ratio		0.19349	0.19541
Tier 1 risk-based capital, ratio		0.19349	0.19541
Total risk-based capital, ratio		0.20603	0.20794
Leverage Ratios [Abstract]
Tier 1 leverage ratio, minimum for capital adequacy plus capital conservation	[1],[2]	0.04000	0.04000
Common equity Tier 1 capital, minimum for capital adequacy plus capital conservation	[1],[2]	0.07000	0.07000
Tier 1 risk-based capital, minimum for capital adequacy plus capital conservation	[1],[2]	0.08500	0.08500
Total risk-based capital, minimum for capital adequacy plus capital conservation	[1],[2]	0.10500	0.10500
Common equity Tier 1 capital conservation buffer		0.0250	0.0250
Tier 1 risk based capital ratio, capital conservation buffer		0.0250	0.0250
Total risk based capital ratio, capital conservation buffer		0.0250	0.0250

[1] Federal regulatory minimum requirements to be considered to be Well Capitalized and Adequately Capitalized

[2] The March 31, 2022 and December 31, 2021 common equity tier 1, tier 1 risk-based, and total risk-based capital ratios include a capital conservation buffer of 2.50 percent