CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 11,856	$ 10,842	$ 33,106	$ 31,743
Unrealized gains and losses:
Unrealized holding (losses) gains on available-for-sale securities arising during the period	(523)	108	1,551	(1,196)
Tax effect	187	(39)	(634)	485
Net of tax	(336)	69	917	(711)
Unrealized gains on securities transferred from held-to-maturity to available-for-sale the period	10,069		10,069
Tax effect	(3,815)		(3,815)
Net of tax	6,254		6,254
Reclassification adjustment for realized gains included in net income	(4,131)	(2,067)	(4,234)	(2,793)
Tax effect	1,640	794	1,682	1,091
Net of tax	(2,491)	(1,273)	(2,552)	(1,702)
Amortization of unrealized net losses on held-to-maturity securities transferred from available-for-sale securities	1,890	37	1,986	165
Tax effect	(774)	(15)	(813)	(67)
Net of tax	1,116	22	1,173	98
Unrealized gains (losses) on cash flow hedges	644	(855)	(1,081)	(1,153)
Tax effect	(263)	349	441	471
Net of tax	381	(506)	(640)	(682)
Unrealized pension plan gains and losses:
Unrealized pension plan gains (losses) before reclassifications		75	(1)	862
Tax effect		(31)		(353)
Net of tax		44	(1)	509
Reclassification adjustment for realized losses included in net income	204	108	306	324
Tax effect	(83)	(44)	(124)	(132)
Net of tax	121	64	182	192
Total other comprehensive income (loss)	5,045	(1,580)	5,333	(2,296)
Total comprehensive income	$ 16,901	$ 9,262	$ 38,439	$ 29,447