Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net			$ 16,674	$ 2,132
Total before tax	$ 44,777	$ 63,818	62,635	120,474
Income tax provision	(8,195)	(12,094)	(11,425)	(22,879)
Compensation and employee benefits	46,043	52,015	100,885	104,100
Net income	36,582	51,724	51,210	97,595
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Available-for-Sale Debt Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment securities gains, net	0	285	249	2,132
Total before tax	0	285	249	2,132
Income tax provision	0	(66)	(58)	(496)
Net income	0	219	191	1,636
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains and Losses on Pension Plan Liability [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	(103)	(80)	(207)	(159)
Income tax provision	24	19	48	37
Compensation and employee benefits	(103)	(80)	(207)	(159)
Net income	(79)	(61)	(159)	(122)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized gains and losses from hedging instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total before tax	2,190	0	3,130	0
Income tax provision	(510)	0	(728)	0
Net income	1,680	0	2,402	0
Interest income, Loans	$ 2,190	$ 0	$ 3,130	$ 0