Accumulated Other Comprehensive Income (Loss) (AOCI Reclass to IS) (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	$ (46,576)	$ (45,530)	$ (143,966)	$ (137,508)
Tax Benefit (Expense)	(14,948)	(20,195)	(53,647)	(54,577)
Net Income	34,276	41,769	117,872	121,851
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Net Income	(842)	(60)	(1,576)	70
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	(1,217)	160	(1,702)	825
Tax Benefit (Expense)	479	(63)	670	(325)
Net Income	(738)	97	(1,032)	500
Sale of Investment Securities Available-for-Sale | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Available-for-sale Securities, Gross Realized Gain (Loss)	189	0	189	64
Tax Benefit (Expense)	(74)	0	(74)	(25)
Net Income	115	0	115	39
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	(362)	(258)	(1,088)	(774)
Tax Benefit (Expense)	143	101	429	305
Net Income	(219)	(157)	(659)	(469)
Prior Service Credit | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	81	81	242	242
Net Actuarial Losses | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and Benefits	$ (443)	$ (339)	$ (1,330)	$ (1,016)