Statement of Comprehensive Income (Statement) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent [Abstract]
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	$ 1,487	$ 1,075	$ 455
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	(1,511)	4,046	9,241
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax, Total	(2,998)	2,971	8,786
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	(333)	(2,024)	1,184
Other Comprehensive Income (Loss), Transfers from Held-to-maturity to Available-for-Sale Securities, Net of Tax	19,095	0	0
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	18,227	(17,586)	1,261
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	37,655	(15,562)	77
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	(454)	0	0
Other Comprehensive Income (Loss), Net of Tax	40,199	(18,533)	(8,709)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest, Total	142,899	91,854	75,533
Net Income (Loss) Attributable to Parent	$ 102,700	$ 110,387	$ 84,242