Other Comprehensive Income - Summary of Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Unrealized (losses)/gains on available for sale securities, before tax amount
Unrealized holding (losses)/gains arising during the period, before tax amount	$ 1,909	$ (550)	$ 3,334	$ (2,228)
Reclassification adjustment for (gains)/losses recognized in net income, before tax amount	(6)	(2)	81	(2)
Derivatives, before tax amount
Change in interest rate contracts, before tax amount	1,696		1,654
Defined benefit retirement plans, before tax amount
Change in retirement liability, before tax amount	36	15	72	29
Total Other Comprehensive (Loss)/Income, before tax amount	3,635	(537)	5,141	(2,201)
Unrealized (losses)/gains on available for sale securities, tax (expense) or benefit
Unrealized holding (losses)/gains arising during the period, tax (expense) or benefit	(456)	127	(786)	453
Reclassification adjustment for (gains)/losses recognized in net income, tax (expense) or benefit	2		(19)
Derivatives, tax (expense) or benefit
Change in interest rate contracts, tax (expense) or benefit	(477)		(465)
Defined benefit retirement plans, tax (expense) or benefit
Change in retirement liability, tax (expense) or benefit	(10)	(5)	(20)	(9)
Total Other Comprehensive (Loss)/Income, tax (expense) or benefit	(941)	122	(1,290)	444
Unrealized (losses)/gains on available for sale securities, net-of-tax amount
Unrealized holding (losses)/gains arising during the period, net-of-tax amount	1,453	(423)	2,548	(1,775)
Reclassification adjustment for (gains)/losses recognized in net income, net-of-tax amount	(4)	(2)	62	(2)
Derivatives, net-of-tax amount
Change in interest rate contracts, net-of-tax amount	1,219		1,189
Defined benefit retirement plans, net-of-tax amount
Change in retirement liability, net-of-tax amount	26	10	52	20
Other comprehensive income/(loss)	$ 2,694	$ (415)	$ 3,851	$ (1,757)