Allowance for Credit Losses (Changes in Allowance for Credit Losses) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
LOANS AND LEASES
Balance at Beginning of Period	$ 136,300,000	$ 165,400,000	$ 138,400,000	$ 190,700,000
Charge-Offs	0	0	(100,000)	(400,000)
Recoveries	5,500,000	3,200,000	8,800,000	4,500,000
Net Recoveries (Charge-Offs)	5,500,000	3,200,000	8,700,000	4,100,000
Provision for Credit Losses	(3,600,000)	(19,800,000)	(8,900,000)	(46,000,000.0)
Balance at End of Period	138,200,000	148,800,000	138,200,000	148,800,000
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	37,500,000	55,100,000	34,100,000	61,100,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	6,000,000.0	(8,600,000)	9,400,000	(14,600,000)
Balance at End of Period	43,500,000	46,500,000	43,500,000	46,500,000
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	14,600,000	8,600,000	11,200,000	7,300,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	800,000	1,900,000	4,200,000	3,200,000
Balance at End of Period	15,400,000	10,500,000	15,400,000	10,500,000
OTHER FINANCIAL ASSETS
Balance at Beginning of Period	1,100,000	1,700,000	1,000,000.0	800,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
Provision for Credit Losses	0	(500,000)	100,000	400,000
Balance at End of Period	1,100,000	1,200,000	1,100,000	1,200,000
TOTAL
Balance at Beginning of Period	189,500,000	230,800,000	184,700,000	259,900,000
Charge-Offs	0	0	(100,000)	(400,000)
Recoveries	5,500,000	3,200,000	8,800,000	4,500,000
Net Recoveries (Charge-Offs)	5,500,000	3,200,000	8,700,000	4,100,000
Provision for credit losses	3,200,000	(27,000,000.0)	4,800,000	(57,000,000.0)
Balance at End of Period	198,200,000	207,000,000.0	198,200,000	207,000,000.0
Corporate Debt
HELD TO MATURITY DEBT SECURITIES
Balance at Beginning of Period	1,600,000	1,100,000	1,400,000	800,000
Provision for Credit Losses	200,000	500,000	400,000	800,000
Balance at End of Period	1,800,000	1,600,000	1,800,000	1,600,000
TOTAL
Provision for credit losses	$ 1,300,000	$ 0	$ 1,700,000	$ 0