Other Comprehensive Income (Loss) - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain on securities transactions	$ 0	$ 339	$ 370	$ 465
Other non-interest expense	4,120	3,260	8,908	5,710
Income before income tax expense	19,700	15,665	28,717	34,091
Income (tax) benefit	(4,603)	(3,634)	(6,855)	(7,141)
Net of tax	15,097	12,031	21,862	26,950
Accumulated Other Comprehensive Income (Loss) Components
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense	(1,071)	(586)	(1,772)	(1,384)
Income (tax) benefit	226	115	369	283
Net of tax	(845)	(471)	(1,403)	(1,101)
Accumulated Other Comprehensive Income (Loss) Components | Reclassification adjustment for gains included in net income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Gain on securities transactions	0	339	370	465
Accumulated Other Comprehensive Income (Loss) Components | Reclassification adjustment of actuarial net (loss) included in net income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other non-interest expense	$ (1,071)	$ (925)	$ (2,142)	$ (1,849)