Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Condensed Consolidated Statements of Comprehensive Income
Net income	$ 40,459	$ 31,823	$ 82,785	$ 50,087
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	(8,216)	1,803	(30,298)	6,920
Tax effect	1,807	(688)	6,697	(2,638)
Reclassification adjustment for (gains) losses included in net income	641	(110)	641	(110)
Tax effect	(141)	43	(141)	42
Net of tax amount	(5,909)	1,048	(23,101)	4,214
Unrealized gains (losses) on derivative financial instruments qualifying as cash flow hedges:
Unrealized holding gains (losses) arising during period	8	18	44	(60)
Tax effect	(2)	(7)	(10)	23
Reclassification adjustment for losses included in interest expense	39	19	87	168
Tax effect	(8)	(7)	(19)	(64)
Net of tax amount	37	23	102	67
Change in pension plan obligation:
Reclassification adjustment for changes included in net income	194	187	387	376
Tax effect	(43)	(71)	(85)	(143)
Net of tax amount	151	116	302	233
Net comprehensive income (loss)	(5,721)	1,187	(22,697)	4,514
Comprehensive income	$ 34,738	$ 33,010	$ 60,088	$ 54,601