Accumulated Other Comprehensive Income (Reclassification out of AOCI) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loan interest income	$ 132,540	$ 124,726	$ 381,996	$ 368,999
Income before income taxes	66,491	54,683	200,468	117,318
Income tax provision	(13,474)	(9,949)	(40,559)	(21,374)
Net Income	53,017	44,734	159,909	95,944
Compensation and employee benefits	54,679	55,133	159,865	156,018
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]
Debt Securities, Available-for-sale, Unrealized Gain (Loss)	0	0	314	249
Income before income taxes	606	0	1,370	249
Income tax provision	(141)	0	(319)	(58)
Net Income	465	0	1,051	191
Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of unrealized gains and losses related to available for sale securities transfer
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loan interest income	606	0	1,056	0
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]
Income before income taxes	(149)	(104)	(448)	(311)
Income tax provision	35	24	104	72
Net Income	(114)	(80)	(344)	(239)
Compensation and employee benefits	(149)	(104)	(448)	(311)
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]
Income before income taxes	2,631	2,673	7,809	5,803
Income tax provision	(612)	(621)	(1,815)	(1,349)
Net Income	2,019	2,052	5,994	4,454
Loans	$ 2,631	$ 2,673	$ 7,809	$ 5,803