Allowance for Credit Losses (Changes in Allowance for Credit Losses Related to Loans) (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
LOANS
Balance at Beginning of Period	$ 159,900,000	$ 136,300,000	$ 144,300,000	$ 138,400,000
Balance at End of Period	152,500,000	138,200,000	152,500,000	138,200,000
Charge-Offs	800,000	0	4,800,000	100,000
Recoveries	800,000	5,500,000	1,900,000	8,800,000
Net Recoveries (Charge-Offs)	0	5,500,000	(2,900,000)	8,700,000
(Release of) Provision for Credit Losses	(7,400,000)	(3,600,000)	11,100,000	(8,900,000)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	34,300,000	37,500,000	38,500,000	34,100,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
(Release of) Provision for Credit Losses	(8,300,000)	6,000,000.0	(12,500,000)	9,400,000
Balance at End of Period	26,000,000.0	43,500,000	26,000,000.0	43,500,000
COMMERCIAL
LOANS
Balance at Beginning of Period	130,800,000	102,500,000	116,200,000	105,600,000
Balance at End of Period	124,000,000.0	102,500,000	124,000,000.0	102,500,000
Charge-Offs	0	0	4,000,000.0	0
Recoveries	100,000	200,000	100,000	2,400,000
Net Recoveries (Charge-Offs)	100,000	200,000	(3,900,000)	2,400,000
(Release of) Provision for Credit Losses	(6,900,000)	(200,000)	11,700,000	(5,500,000)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	31,300,000	34,700,000	36,300,000	31,400,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
(Release of) Provision for Credit Losses	(8,000,000.0)	5,600,000	(13,000,000.0)	8,900,000
Balance at End of Period	23,300,000	40,300,000	23,300,000	40,300,000
PERSONAL
LOANS
Balance at Beginning of Period	29,100,000	33,800,000	28,100,000	32,800,000
Balance at End of Period	28,500,000	35,700,000	28,500,000	35,700,000
Charge-Offs	800,000	0	800,000	100,000
Recoveries	700,000	5,300,000	1,800,000	6,400,000
Net Recoveries (Charge-Offs)	(100,000)	5,300,000	1,000,000.0	6,300,000
(Release of) Provision for Credit Losses	(500,000)	(3,400,000)	(600,000)	(3,400,000)
UNDRAWN LOAN COMMITMENTS AND STANDBY LETTERS OF CREDIT
Balance at Beginning of Period	3,000,000.0	2,800,000	2,200,000	2,700,000
Charge-Offs	0	0	0	0
Recoveries	0	0	0	0
Net Recoveries (Charge-Offs)	0	0	0	0
(Release of) Provision for Credit Losses	(300,000)	400,000	500,000	500,000
Balance at End of Period	$ 2,700,000	$ 3,200,000	$ 2,700,000	$ 3,200,000