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	$ 225,913	$ 219,602	$ 184,672
Other Comprehensive Income (Loss), Net of Tax:
Net Unrealized Gains (Losses) on Investment Securities	22,677	(6,525)	(1,986)
Defined Benefit Plans, Net	(2,746)	(2,326)	1,177
Other Comprehensive Income (Loss)	19,931	(8,851)	(809)
Comprehensive Income	$ 245,844	$ 210,751	$ 183,863