Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Condensed Consolidated Statements of Comprehensive Income
Net income	$ 42,326	$ 18,264
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	(22,082)	5,116
Tax effect	4,890	(1,950)
Net of tax amount	(17,192)	3,166
Unrealized gains (losses) on derivative financial instruments qualifying as cash flow hedges:
Unrealized holding gains (losses) arising during period	36	(38)
Tax effect	(8)	14
Reclassification adjustment for losses included in interest expense	47	110
Tax effect	(10)	(42)
Net of tax amount	65	44
Change in pension plan obligation:
Reclassification adjustment for changes included in net income	194	188
Tax effect	(43)	(71)
Net of tax amount	151	117
Net comprehensive income (loss)	(16,976)	3,327
Comprehensive income	$ 25,350	$ 21,591