Segment and Related Information - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Interest income	$ 63,984	$ 57,772	$ 186,267	$ 167,735
Interest expense	10,821	6,772	27,703	18,400
Net Interest Income	53,163	51,000	158,564	149,335
Provision for loan and lease losses	272	402	1,884	2,147
Noninterest income	18,603	17,202	57,591	51,892
Noninterest expense	45,133	41,883	133,839	124,819
Income Before Income Tax Expense	26,361	25,917	80,432	74,261
Income tax expense	5,427	8,491	16,939	24,127
Net Income Attributable to Noncontrolling Interests and Tompkins Financial Corporation	20,934	17,426	63,493	50,134
Less: Net Income Attributable to Noncontrolling Interests	32	32	96	97
Net Income Attributable to Tompkins Financial Corporation	20,902	17,394	63,397	50,037
Depreciation and amortization	2,319	2,041	6,937	5,666
Assets	6,746,960	6,524,060	6,746,960	6,524,060	$ 6,648,290
Goodwill	92,283	92,291	92,283	92,291	92,291
Other intangibles, net	7,989	9,750	7,989	9,750	9,263
Net loans and leases	4,761,351	4,452,475	4,761,351	4,452,475	4,629,349
Deposits	5,025,082	4,943,944	5,025,082	4,943,944	4,837,807
Total Equity	599,144	589,868	599,144	589,868	$ 576,202	$ 549,405
Operating Segments | Banking
Segment Reporting Information [Line Items]
Interest income	63,984	57,772	186,267	167,735
Interest expense	10,822	6,772	27,705	18,401
Net Interest Income	53,162	51,000	158,562	149,334
Provision for loan and lease losses	272	402	1,884	2,147
Noninterest income	6,777	5,795	23,131	18,917
Noninterest expense	36,077	32,876	107,120	98,182
Income Before Income Tax Expense	23,590	23,517	72,689	67,922
Income tax expense	4,737	7,635	15,040	21,816
Net Income Attributable to Noncontrolling Interests and Tompkins Financial Corporation	18,853	15,882	57,649	46,106
Less: Net Income Attributable to Noncontrolling Interests	32	32	96	97
Net Income Attributable to Tompkins Financial Corporation	18,821	15,850	57,553	46,009
Depreciation and amortization	2,252	1,963	6,727	5,402
Assets	6,697,701	6,479,292	6,697,701	6,479,292
Goodwill	64,370	64,370	64,370	64,370
Other intangibles, net	4,415	5,474	4,415	5,474
Net loans and leases	4,761,351	4,452,475	4,761,351	4,452,475
Deposits	5,036,934	4,955,033	5,036,934	4,955,033
Total Equity	548,330	544,417	548,330	544,417
Operating Segments | Insurance
Segment Reporting Information [Line Items]
Interest income	1	0	2	1
Interest expense	0	0	0	0
Net Interest Income	1	0	2	1
Provision for loan and lease losses	0	0	0	0
Noninterest income	7,998	7,729	22,974	22,177
Noninterest expense	6,397	6,204	18,918	18,343
Income Before Income Tax Expense	1,602	1,525	4,058	3,835
Income tax expense	422	572	1,046	1,475
Net Income Attributable to Noncontrolling Interests and Tompkins Financial Corporation	1,180	953	3,012	2,360
Less: Net Income Attributable to Noncontrolling Interests	0	0	0	0
Net Income Attributable to Tompkins Financial Corporation	1,180	953	3,012	2,360
Depreciation and amortization	56	64	174	221
Assets	41,910	40,791	41,910	40,791
Goodwill	19,702	19,710	19,702	19,710
Other intangibles, net	3,345	3,979	3,345	3,979
Net loans and leases	0	0	0	0
Deposits	0	0	0	0
Total Equity	33,248	31,615	33,248	31,615
Operating Segments | Wealth Management
Segment Reporting Information [Line Items]
Interest income	0	0	0	0
Interest expense	0	0	0	0
Net Interest Income	0	0	0	0
Provision for loan and lease losses	0	0	0	0
Noninterest income	4,345	4,130	12,960	12,056
Noninterest expense	3,176	3,255	9,275	9,552
Income Before Income Tax Expense	1,169	875	3,685	2,504
Income tax expense	268	284	853	836
Net Income Attributable to Noncontrolling Interests and Tompkins Financial Corporation	901	591	2,832	1,668
Less: Net Income Attributable to Noncontrolling Interests	0	0	0	0
Net Income Attributable to Tompkins Financial Corporation	901	591	2,832	1,668
Depreciation and amortization	11	14	36	43
Assets	19,703	16,579	19,703	16,579
Goodwill	8,211	8,211	8,211	8,211
Other intangibles, net	229	297	229	297
Net loans and leases	0	0	0	0
Deposits	0	0	0	0
Total Equity	17,566	13,836	17,566	13,836
Intercompany
Segment Reporting Information [Line Items]
Interest income	(1)	0	(2)	(1)
Interest expense	(1)	0	(2)	(1)
Net Interest Income	0	0	0	0
Provision for loan and lease losses	0	0	0	0
Noninterest income	(517)	(452)	(1,474)	(1,258)
Noninterest expense	(517)	(452)	(1,474)	(1,258)
Income Before Income Tax Expense	0	0	0	0
Income tax expense	0	0	0	0
Net Income Attributable to Noncontrolling Interests and Tompkins Financial Corporation	0	0	0	0
Less: Net Income Attributable to Noncontrolling Interests	0	0	0	0
Net Income Attributable to Tompkins Financial Corporation	0	0	0	0
Depreciation and amortization	0	0	0	0
Assets	(12,354)	(12,602)	(12,354)	(12,602)
Goodwill	0	0	0	0
Other intangibles, net	0	0	0	0
Net loans and leases	0	0	0	0
Deposits	(11,852)	(11,089)	(11,852)	(11,089)
Total Equity	$ 0	$ 0	$ 0	$ 0