Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Condensed Consolidated Statements of Comprehensive Income
Net income	$ 35,046	$ 28,095	$ 85,133	$ 77,105
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	130	(4,388)	7,049	12,162
Tax effect	(50)	1,673	(2,687)	(4,638)
Reclassification adjustment for (gains) losses included in net income	(525)		(635)	(122)
Tax effect	200		242	47
Net of tax amount	(245)	(2,715)	3,969	7,449
Unrealized losses on derivative financial instruments qualifying as cash flow hedges:
Unrealized holding losses arising during period	4	51	(56)	(147)
Tax effect	(1)	(19)	21	56
Reclassification adjustment for losses included in interest expense	57	69	226	209
Tax effect	(22)	(27)	(86)	(80)
Net of tax amount	38	74	105	38
Change in pension plan obligation:
Reclassification adjustment for changes included in net income	188	204	564	612
Tax effect	(72)	(78)	(215)	(233)
Net of tax amount	116	126	349	379
Other comprehensive income (loss), net of tax	(91)	(2,515)	4,423	7,866
Comprehensive income	$ 34,955	$ 25,580	$ 89,556	$ 84,971