CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 21,696	$ 19,902	$ 52,612	$ 41,680
Unrealized gains and losses:
Unrealized holding gains (losses) on available-for-sale securities arising during the period	2,236	(2,840)	11,821	(9,639)
Tax effect	(584)	729	(3,061)	2,466
Net of tax	1,652	(2,111)	8,760	(7,173)
Reclassification adjustment for realized losses included in net income	279		280
Tax effect	(62)		(62)
Net of tax	217		218
Unrealized (losses) gains on cash flow hedges	(49)	14	(977)	1,108
Tax effect	27	(5)	309	(312)
Net of tax	(22)	9	(668)	796
Reclassification adjustment for gains included in net income	(204)		(563)
Tax effect	46		125
Net of tax	(158)		(438)
Unrealized pension plan gains and losses:
Unrealized pension plan (losses) gains before reclassifications			(562)	236
Tax effect			158	(67)
Net of tax			(404)	169
Reclassification adjustment for amortization included in net income	90	91	269	274
Tax effect	(26)	(26)	(76)	(77)
Net of tax	64	65	193	197
Total other comprehensive income (loss)	1,753	(2,037)	7,661	(6,011)
Total comprehensive income	$ 23,449	$ 17,865	$ 60,273	$ 35,669