CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 19,902	$ 13,077	$ 41,680	$ 32,640
Unrealized gains and losses:
Unrealized holding (losses) gains on available-for-sale securities arising during the period	(2,840)	415	(9,639)	1,332
Tax effect	729	(165)	2,466	(525)
Net of tax	(2,111)	250	(7,173)	807
Reclassification adjustment for realized gains included in net income				(1,596)
Tax effect				579
Net of tax				(1,017)
Unrealized gains (losses) on cash flow hedges	14	119	1,108	76
Tax effect	(5)	(48)	(312)	(31)
Net of tax	9	71	796	45
Unrealized pension plan gains (losses):
Unrealized pension plan gains (losses) before reclassifications			236	(2)
Tax effect			(67)	1
Net of tax			169	(1)
Reclassification adjustment for amortization included in net income	91	103	274	309
Tax effect	(26)	(42)	(77)	(126)
Net of tax	65	61	197	183
Total other comprehensive (loss) income	(2,037)	382	(6,011)	17
Total comprehensive income	$ 17,865	$ 13,459	$ 35,669	$ 32,657