Loans (Credit Quality Indicators Vintage) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	$ 103,774		$ 878,981
Term loans amortized cost, prior year	868,364		1,551,627
Term loans amortized cost, two years ago	1,557,431		1,144,330
Term loans amortized cost, three years ago	1,131,395		478,623
Term loans amortized cost, four years ago	472,621		372,009
Term loans amortized cost, five years ago or more	1,156,854		831,226
Revolving loans amortized cost	379,704		375,764
Revolving loans converted to term loans	15,089		15,146
Total	5,685,232		5,647,706
Gross charge-offs, current year	66		196
Gross charge-offs, prior year	0		0
Gross charge-offs, two years ago	0		8
Gross charge-offs, three years ago	0		0
Gross charge-offs, four years ago	2		0
Gross charge-offs, five years ago or more	2		373
Gross charge-offs, revolving loans	0		0
Gross charge-offs, revolving loans converted to term loans	0		0
Total gross charge-offs	70	$ 61	577
Commercial Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	39,504		348,969
Term loans amortized cost, prior year	359,048		598,946
Term loans amortized cost, two years ago	606,664		414,898
Term loans amortized cost, three years ago	415,435		168,451
Term loans amortized cost, four years ago	167,540		181,982
Term loans amortized cost, five years ago or more	524,795		349,986
Revolving loans amortized cost	44,510		42,095
Revolving loans converted to term loans	1,022		1,032
Total	2,158,518		2,106,359
Gross charge-offs, current year	0		0
Gross charge-offs, prior year	0		0
Gross charge-offs, two years ago	0		0
Gross charge-offs, three years ago	0		0
Gross charge-offs, four years ago	0		0
Gross charge-offs, five years ago or more	0		373
Gross charge-offs, revolving loans	0		0
Gross charge-offs, revolving loans converted to term loans	0		0
Total gross charge-offs	0	0	373
Commercial Real Estate | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	39,504		327,139
Term loans amortized cost, prior year	337,357		598,946
Term loans amortized cost, two years ago	606,664		396,468
Term loans amortized cost, three years ago	396,089		168,451
Term loans amortized cost, four years ago	167,540		167,484
Term loans amortized cost, five years ago or more	494,029		333,356
Revolving loans amortized cost	44,510		42,095
Revolving loans converted to term loans	1,022		1,032
Total	2,086,715		2,034,971
Commercial Real Estate | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	0		0
Term loans amortized cost, prior year	13,716		0
Term loans amortized cost, two years ago	0		0
Term loans amortized cost, three years ago	0		0
Term loans amortized cost, four years ago	0		0
Term loans amortized cost, five years ago or more	16,536		16,630
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	30,252		16,630
Commercial Real Estate | Classified [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	0		21,830
Term loans amortized cost, prior year	7,975		0
Term loans amortized cost, two years ago	0		18,430
Term loans amortized cost, three years ago	19,346		0
Term loans amortized cost, four years ago	0		14,498
Term loans amortized cost, five years ago or more	14,230		0
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	41,551		54,758
Commercial & Industrial
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	41,752		66,726
Term loans amortized cost, prior year	53,657		125,712
Term loans amortized cost, two years ago	130,711		52,471
Term loans amortized cost, three years ago	51,624		49,812
Term loans amortized cost, four years ago	49,053		73,739
Term loans amortized cost, five years ago or more	189,563		145,361
Revolving loans amortized cost	96,460		90,664
Revolving loans converted to term loans	556		587
Total	613,376		605,072
Gross charge-offs, current year	8		37
Gross charge-offs, prior year	0		0
Gross charge-offs, two years ago	0		0
Gross charge-offs, three years ago	0		0
Gross charge-offs, four years ago	0		0
Gross charge-offs, five years ago or more	0		0
Gross charge-offs, revolving loans	0		0
Gross charge-offs, revolving loans converted to term loans	0		0
Total gross charge-offs	8	11	37
Commercial & Industrial | Pass [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	41,752		55,607
Term loans amortized cost, prior year	53,657		124,894
Term loans amortized cost, two years ago	125,752		52,282
Term loans amortized cost, three years ago	50,132		49,812
Term loans amortized cost, four years ago	49,053		72,876
Term loans amortized cost, five years ago or more	184,526		145,361
Revolving loans amortized cost	96,460		90,664
Revolving loans converted to term loans	556		587
Total	601,888		592,083
Commercial & Industrial | Special Mention [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	0		11,119
Term loans amortized cost, prior year	0		0
Term loans amortized cost, two years ago	4,141		0
Term loans amortized cost, three years ago	1,309		0
Term loans amortized cost, four years ago	0		181
Term loans amortized cost, five years ago or more	4,369		0
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	9,819		11,300
Commercial & Industrial | Classified [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	0		0
Term loans amortized cost, prior year	0		818
Term loans amortized cost, two years ago	818		189
Term loans amortized cost, three years ago	183		0
Term loans amortized cost, four years ago	0		682
Term loans amortized cost, five years ago or more	668		0
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	1,669		1,689
Residential Real Estate
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	17,794		431,563
Term loans amortized cost, prior year	426,177		808,442
Term loans amortized cost, two years ago	801,966		666,447
Term loans amortized cost, three years ago	655,038		256,440
Term loans amortized cost, four years ago	252,241		114,056
Term loans amortized cost, five years ago or more	432,308		327,530
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	2,585,524		2,604,478
Gross charge-offs, current year	0		0
Gross charge-offs, prior year	0		0
Gross charge-offs, two years ago	0		0
Gross charge-offs, three years ago	0		0
Gross charge-offs, four years ago	0		0
Gross charge-offs, five years ago or more	0		0
Gross charge-offs, revolving loans	0		0
Gross charge-offs, revolving loans converted to term loans	0		0
Total gross charge-offs	0	0	0
Residential Real Estate | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	17,794		431,563
Term loans amortized cost, prior year	426,177		808,442
Term loans amortized cost, two years ago	801,966		666,447
Term loans amortized cost, three years ago	654,646		255,554
Term loans amortized cost, four years ago	251,358		113,462
Term loans amortized cost, five years ago or more	426,725		320,894
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	2,578,666		2,596,362
Residential Real Estate | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	0		0
Term loans amortized cost, prior year	0		0
Term loans amortized cost, two years ago	0		0
Term loans amortized cost, three years ago	392		886
Term loans amortized cost, four years ago	883		594
Term loans amortized cost, five years ago or more	5,583		6,636
Revolving loans amortized cost	0		0
Revolving loans converted to term loans	0		0
Total	6,858		8,116
Home Equity
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	3,682		24,925
Term loans amortized cost, prior year	23,025		14,997
Term loans amortized cost, two years ago	14,661		6,829
Term loans amortized cost, three years ago	6,713		2,919
Term loans amortized cost, four years ago	2,839		2,112
Term loans amortized cost, five years ago or more	6,374		4,525
Revolving loans amortized cost	238,497		242,760
Revolving loans converted to term loans	13,511		13,527
Total	309,302		312,594
Gross charge-offs, current year	0		0
Gross charge-offs, prior year	0		0
Gross charge-offs, two years ago	0		0
Gross charge-offs, three years ago	0		0
Gross charge-offs, four years ago	0		0
Gross charge-offs, five years ago or more	0		0
Gross charge-offs, revolving loans	0		0
Gross charge-offs, revolving loans converted to term loans	0		0
Total gross charge-offs	0	0	0
Home Equity | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	3,682		24,925
Term loans amortized cost, prior year	23,025		14,997
Term loans amortized cost, two years ago	14,522		6,829
Term loans amortized cost, three years ago	6,690		2,919
Term loans amortized cost, four years ago	2,697		1,982
Term loans amortized cost, five years ago or more	5,984		3,696
Revolving loans amortized cost	237,829		241,459
Revolving loans converted to term loans	11,994		12,591
Total	306,423		309,398
Home Equity | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	0		0
Term loans amortized cost, prior year	0		0
Term loans amortized cost, two years ago	139		0
Term loans amortized cost, three years ago	23		0
Term loans amortized cost, four years ago	142		130
Term loans amortized cost, five years ago or more	390		829
Revolving loans amortized cost	668		1,301
Revolving loans converted to term loans	1,517		936
Total	2,879		3,196
Other
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	1,042		6,798
Term loans amortized cost, prior year	6,457		3,530
Term loans amortized cost, two years ago	3,429		3,685
Term loans amortized cost, three years ago	2,585		1,001
Term loans amortized cost, four years ago	948		120
Term loans amortized cost, five years ago or more	3,814		3,824
Revolving loans amortized cost	237		245
Revolving loans converted to term loans	0		0
Total	18,512		19,203
Gross charge-offs, current year	58		159
Gross charge-offs, prior year	0		0
Gross charge-offs, two years ago	0		8
Gross charge-offs, three years ago	0		0
Gross charge-offs, four years ago	2		0
Gross charge-offs, five years ago or more	2		0
Gross charge-offs, revolving loans	0		0
Gross charge-offs, revolving loans converted to term loans	0		0
Total gross charge-offs	62	$ 50	167
Other | Current [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	1,020		6,777
Term loans amortized cost, prior year	6,457		3,530
Term loans amortized cost, two years ago	3,422		3,685
Term loans amortized cost, three years ago	2,585		1,001
Term loans amortized cost, four years ago	945		120
Term loans amortized cost, five years ago or more	3,814		3,824
Revolving loans amortized cost	237		243
Revolving loans converted to term loans	0		0
Total	18,480		19,180
Other | Past Due [Member]
Financing Receivable, Credit Quality Indicator [Line Items]
Term loans amortized cost, current year	22		21
Term loans amortized cost, prior year	0		0
Term loans amortized cost, two years ago	7		0
Term loans amortized cost, three years ago	0		0
Term loans amortized cost, four years ago	3		0
Term loans amortized cost, five years ago or more	0		0
Revolving loans amortized cost	0		2
Revolving loans converted to term loans	0		0
Total	$ 32		$ 23