Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Consolidated Statements of Comprehensive Income (Unaudited) [Abstract]
Net income	$ 12,240	$ 10,464	$ 23,187	$ 20,875
Net unrealized holding gain on securities available for sale	3,343	4,565	4,522	12,600
Reclassification adjustments for net gain recognized in income	0	(668)	0	(668)
Tax effect	(1,337)	(1,559)	(1,809)	(4,773)
Net unrealized gain on securities available for sale, net of tax	2,006	2,338	2,713	7,159
Amortization of net actuarial gain	(73)	(50)	(136)	(17)
Amortization of prior service cost	22	22	45	45
Tax effect	20	12	36	(11)
Amortization of net actuarial gain and prior service cost on pension and postretirement plans, net of tax	(31)	(16)	(55)	17
Other comprehensive income, net of tax	1,975	2,322	2,658	7,176
Comprehensive income	$ 14,215	$ 12,786	$ 25,845	$ 28,051