Other Comprehensive Income (Loss) - Reclassification out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment for gains included in net income	$ 1,256	$ 0	$ 1,721	$ 116
Other non-interest expense	2,217	1,779	7,927	5,024
Income before income tax expense	19,610	17,783	53,702	15,669
Income (tax) benefit	(5,392)	(6,956)	(12,534)	(7,800)
Net of tax	14,218	10,827	41,168	7,869
Accumulated Other Comprehensive Income (Loss) Components
Accumulated Other Comprehensive Income (Loss) [Line Items]
Income before income tax expense	326	0	(1,058)	780
Income (tax) benefit	(96)	3	187	(170)
Net of tax	230	3	(871)	610
Accumulated Other Comprehensive Income (Loss) Components | Reclassification adjustment for gains included in net income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment for gains included in net income	1,256	0	1,721	116
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	$ (930)	$ 0	$ (2,779)	$ 664