Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 14,667	$ 15,405	$ 29,225	$ 30,213
Net unrealized holding gain (loss) on securities available for sale	7,177	(1,669)	11,767	(8,830)
Tax effect	(1,864)	425	(3,058)	2,284
Net unrealized gain (loss) on securities available for sale, net of tax	5,313	(1,244)	8,709	(6,546)
Amortization of net actuarial gain	(20)	(106)	(68)	(178)
Amortization of prior service (credit) cost	(82)	22	(167)	45
Tax effect	26	22	61	35
Amortization of net actuarial gain and prior service credit on pension and postretirement plans, net of tax	(76)	(62)	(174)	(98)
Other comprehensive income (loss), net of tax	5,237	(1,306)	8,535	(6,644)
Comprehensive income	$ 19,904	$ 14,099	$ 37,760	$ 23,569