Fair Value Measurements - Estimated Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair value of financial assets
Securities - held-to-maturity	$ 140,315	$ 142,832
FHLB and FRB stock	50,498	43,133
Financial Liabilities:
Time deposits	748,250	870,788
Securities sold under agreements to repurchase	75,177	69,062
Other borrowings	1,071,742	884,815
Trust preferred debentures	16,691	37,681
(Level 1)
Fair value of financial assets
Cash and cash equivalents	84,303	63,954
Securities - held-to-maturity	0	0
FHLB and FRB stock	0	0
Accrued interest receivable	0	0
Loans and leases, net	0	0
Financial Liabilities:
Time deposits	0	0
Other deposits	0	0
Securities sold under agreements to repurchase	0
Other borrowings	0	0
Trust preferred debentures	0	0
Accrued interest payable	0	0
(Level 2)
Fair value of financial assets
Cash and cash equivalents	0	0
Securities - held-to-maturity	140,315	142,832
FHLB and FRB stock	50,498	43,133
Accrued interest receivable	20,122	17,390
Loans and leases, net	4,617	7,296
Financial Liabilities:
Time deposits	744,310	867,921
Other deposits	4,089,557	3,754,351
Securities sold under agreements to repurchase	75,177	69,109
Other borrowings	1,069,609	884,842
Trust preferred debentures	22,012	43,321
Accrued interest payable	2,054	1,902
(Level 3)
Fair value of financial assets
Cash and cash equivalents	0	0
Securities - held-to-maturity	0
FHLB and FRB stock	0	0
Accrued interest receivable	0	0
Loans and leases, net	4,551,103	4,180,119
Financial Liabilities:
Time deposits	0	0
Other deposits	0	0
Securities sold under agreements to repurchase	0
Other borrowings	0	0
Trust preferred debentures	0	0
Accrued interest payable	0	0
Carrying Amount
Fair value of financial assets
Cash and cash equivalents	84,303	63,954
Securities - held-to-maturity	139,216	142,119
FHLB and FRB stock	50,498	43,133
Accrued interest receivable	20,122	17,390
Loans and leases, net	4,632,288	4,222,278
Financial Liabilities:
Time deposits	748,250	870,788
Other deposits	4,089,557	3,754,351
Securities sold under agreements to repurchase	75,177	69,062
Other borrowings	1,071,742	884,815
Trust preferred debentures	16,691	37,681
Accrued interest payable	2,054	1,902
Carrying Amount | Tompkins Capital Trust I
Financial Liabilities:
Trust preferred debentures		21,200
Fair Value
Fair value of financial assets
Cash and cash equivalents	84,303	63,954
Securities - held-to-maturity	140,315	142,832
FHLB and FRB stock	50,498	43,133
Accrued interest receivable	20,122	17,390
Loans and leases, net	4,555,720	4,187,415
Financial Liabilities:
Time deposits	744,310	867,921
Other deposits	4,089,557	3,754,351
Securities sold under agreements to repurchase	75,177	69,109
Other borrowings	1,069,609	884,842
Trust preferred debentures	22,012	43,321
Accrued interest payable	$ 2,054	$ 1,902