Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 14,808	$ 10,947
Net unrealized holding (loss) gain on securities available for sale	(7,160)	1,179
Tax effect	1,858	(472)
Net unrealized (loss) gain on securities available for sale, net of tax	(5,302)	707
Amortization of net actuarial gain	(72)	(63)
Amortization of prior service cost	23	23
Tax effect	13	16
Amortization of net actuarial gain and prior service cost on pension and postretirement plans, net of tax	(36)	(24)
Other comprehensive (loss) income, net of tax	(5,338)	683
Comprehensive income	$ 9,470	$ 11,630