Accumulated Other Comprehensive Income (Loss) (AOCI Reclass to IS) (Details 3) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Tax Benefit (Expense)	$ (9,759)		$ (15,903)		$ (17,220)	$ (29,563)
Net Income	38,908	$ 34,742	56,919	$ 58,799	73,650	115,718
Salaries and Benefits	(50,715)		(53,511)		(105,178)	(110,097)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Net Income	(463)		(424)		(829)	(1,008)
Reclassification out of Accumulated Other Comprehensive Income | Amortization of Unrealized Gains(Losses) of Investment Securities Transferred from AFS to HTM
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Interest Income	(121)		(368)		(186)	(764)
Tax Benefit (Expense)	32		96		49	201
Net Income	(89)		(272)		(137)	(563)
Reclassification out of Accumulated Other Comprehensive Income | Sale of Investment Securities Available-for-Sale
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Tax Benefit (Expense)	0		(34)		(21)	(17)
Net Income	0		93		56	46
Sale of Investment Securities Available-for-Sale	0		127		77	63
Reclassification out of Accumulated Other Comprehensive Income | Amortization of Defined Benefit Pension Items
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Tax Benefit (Expense)	135		89		270	177
Net Income	(374)		(245)		(748)	(491)
Salaries and Benefits	(509)		(334)		(1,018)	(668)
Reclassification out of Accumulated Other Comprehensive Income | Prior Service Credit
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	62		72		123	144
Reclassification out of Accumulated Other Comprehensive Income | Net Actuarial Losses
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	$ (571)		$ (406)		$ (1,141)	$ (812)