Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Condensed Consolidated Statements of Comprehensive Income
Net income	$ 44,367	$ 42,326
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during period	16,752	(22,082)
Tax effect	(3,686)	4,890
Reclassification adjustment for gains included in net income	541
Tax effect	(119)
Net of tax amount	13,488	(17,192)
Unrealized losses on derivative financial instruments qualifying as cash flow hedges:
Unrealized holding gains (losses) arising during period	(2,651)	36
Tax effect	583	(8)
Reclassification adjustment for gains (losses) included in interest expense	(10)	47
Tax effect	2	(10)
Net of tax amount	(2,076)	65
Change in pension plan obligation:
Reclassification adjustment for changes included in net income	121	194
Tax effect	(26)	(43)
Net of tax amount	95	151
Other comprehensive gain (loss), net of tax	11,507	(16,976)
Comprehensive income	$ 55,874	$ 25,350