Accumulated Other Comprehensive Income (Loss) (AOCI Reclass to IS) (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	$ (54,422)	$ (51,165)
Tax Benefit (Expense)	(10,442)	(21,644)
Net Income	54,040	51,176
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Net Income	(700)	(451)
Amortization of Unrealized Gains(Losses) of Investment Securities Transferred from AFS to HTM | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Interest Income	(659)	(504)
Tax Benefit (Expense)	175	199
Net Income	(484)	(305)
Amortization of Defined Benefit Pension Items | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	(294)	(242)
Tax Benefit (Expense)	78	96
Net Income	(216)	(146)
Prior Service Credit | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	142	81
Net Actuarial Losses | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	$ (436)	$ (323)