Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Consolidated Statements of Comprehensive Income [Abstract]
Net income	$ 14,558	$ 14,808
Net unrealized holding gain (loss) on securities available for sale	4,588	(7,160)
Tax effect	(1,192)	1,858
Net unrealized gain (loss) on securities available for sale, net of tax	3,396	(5,302)
Amortization of net actuarial gain	(48)	(72)
Amortization of prior service (credit) cost	(85)	23
Tax effect	35	13
Amortization of net actuarial gain and prior service credit on pension and postretirement plans, net of tax	(98)	(36)
Other comprehensive income (loss), net of tax	3,298	(5,338)
Comprehensive income	$ 17,856	$ 9,470