Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income Available to Common Shareholders	$ 89,352	$ 70,002	$ 54,310
Available-for-Sale Securities
Unrealized gain (loss) on available-for-sale securities arising during period	27,115	(7,054)	7,396
Reclassification adjustment for net (gains) losses	(69)	90	(4,476)
Other comprehensive income (loss) related to available-for-sale securities	27,046	(6,964)	2,920
Defined Benefit Pension Plan
Amortization of actuarial net gains	917	890	849
Recognition of unrealized losses	(1,447)	(1,982)	(11)
Change in underfunded pension liability	(530)	(1,092)	838
Other comprehensive income (loss) before income taxes	26,516	(8,056)	3,758
Tax effect	(6,194)	1,875	(1,391)
Other comprehensive income (loss), net of tax	20,322	(6,181)	2,367
Comprehensive income, net of tax	$ 109,674	$ 63,821	$ 56,677