Income Taxes - The Components of the Net Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
Postretirement benefits	$ 7,600	$ 7,188
Allowance for loan losses	13,886	6,782
Operating lease liabilities	18,175	12,863
Stock based compensation	2,845	2,950
Depreciation	2,002	1,875
Unrealized loss on securities available for sale		1,812
Fair value adjustment on financial assets carried at fair value	23	95
Fair value hedges	2,726	1,669
Adjustment required to recognize funded status of postretirement pension plans	837	447
Cashflow hedges	7,780	2,668
Deferred loan income	2,000	1,367
Fair Value of Loans from Empire acquisition	3,465
Net operating loss (NYS)	23
Net operating loss (NYC)	1,395	880
Other	3,412	1,690
Deferred tax assets	66,169	42,286
Deferred tax liabilities:
FPFC deferred income	2,084	2,256
Right of Use Asset	15,582	12,863
Fair value adjustment on financial liabilities carried at fair value	4,968	5,003
Entity specific fair value	821	456
Unrealized losses on securities	573
Deferred loan cost	6,426	5,994
Other	1,459	341
Deferred tax liabilities	31,913	26,913
Net deferred tax asset included in other assets	$ 34,256	$ 15,373