Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income		$ 28,476	$ 40,067	$ 20,952
Net change in unrealized losses on available-for-sale securities:
Net change in unrealized losses on available-for-sale securities, net of tax of $1,017, $1,212, and $1,873, respectively		(1,888)	(2,251)	(3,479)
Net reclassification adjustment for gains included in net income, net of tax of $18, $1, and $158, respectively	[1]	(556)	(33)	(3)
Net change in unrealized losses on available-for-sale securities, net of tax		(2,444)	(2,284)	(3,482)
Net change in unrealized gains (losses) on cash flow hedging derivatives:
Net change in unrealized losses on cash flow hedging derivatives, net of tax of $134, $343, and $825, respectively		(248)	(637)	(1,533)
Net reclassification adjustment for effective portion of cash flow hedges included in interest expense, net of tax of ($709), ($593), and ($600), respectively	[2]	1,035	1,317	1,102
Net change in unrealized gains (losses) on cash flow hedging derivatives, net of tax		787	680	(431)
Postretirement plans:
Net actuarial loss, net of tax of $723, $127, and $21, respectively		(1,342)	(235)	(39)
Reclassification of amortization of net unrecognized actuarial loss and of prior service cost included in net periodic cost, net of tax of ($83), ($84), and ($51), respectively	[3]	170	152	155
Net gain (loss) on postretirement plans, net of tax		(1,172)	(83)	116
Other comprehensive loss		(2,829)	(1,687)	(3,797)
Comprehensive income		$ 25,647	$ 38,380	$ 17,155

[1] (1) Reclassified into the consolidated statements of income within net gain on sale of securities.

[2] (2)Reclassified into the consolidated statements of income within interest on borrowings and subordinated debentures.

[3] (3) Reclassified into the consolidated statements of income within salaries and employee benefits.