Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 14,708	$ 15,199	$ 43,933	$ 45,412
Net unrealized holding gain (loss) on securities available for sale	2,418	(4,079)	14,185	(12,908)
Tax effect	(628)	1,069	(3,686)	3,352
Net unrealized gain (loss) on securities available for sale, net of tax	1,790	(3,010)	10,499	(9,556)
Amortization of net actuarial gain	(35)	(189)	(103)	(367)
Amortization of prior service (credit) cost	(83)	(73)	(250)	(28)
Tax effect	31	68	92	103
Amortization of net actuarial gain and prior service credit on pension and postretirement plans, net of tax	(87)	(194)	(261)	(292)
Other comprehensive income (loss), net of tax	1,703	(3,204)	10,238	(9,848)
Comprehensive income	$ 16,411	$ 11,995	$ 54,171	$ 35,564