Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block]

	As of December 31,
	2021			2020
	(In thousands)
Type of Loans:
Commercial loans	$	2,982,399		$	2,836,833
Real estate construction loans		611,031			679,492
Commercial mortgage loans		8,143,272			7,555,027
Residential mortgage loans		4,182,006			4,145,389
Equity lines		419,487			424,555
Installment and other loans		4,284			3,100
Gross loans		16,342,479			15,644,396
Less:
Allowance for loan losses		(136,157	)		(166,538	)
Unamortized deferred loan fees		(4,321	)		(2,494	)
Total loans, net	$	16,202,001		$	15,475,364

Impaired Financing Receivables [Table Text Block]

	For the year ended December 31, 2021
	Average Recorded Investment		Interest Income Recognized
	(In thousands)
Commercial loans	$	21,453	$	—
Real estate construction loans		3,805		—
Commercial mortgage loans		38,047		1,044
Residential mortgage and equity lines		9,435		30
Total	$	72,740	$	1,074

	For the year ended December 31, 2020
	Average Recorded Investment		Interest Income Recognized
	(In thousands)
Commercial loans	$	31,009	$	246
Real estate construction loans		4,408		294
Commercial mortgage loans		41,649		1,602
Residential mortgage and equity lines		14,287		252
Total	$	91,353	$	2,394

Financing Receivable, Nonaccrual [Table Text Block]

	As of December 31,
	2021		2020		2019
	(In thousands)
Non-accrual portfolio loans	$	65,846	$	67,684	$	40,523
Contractual interest due		4,032		3,093		1,775
Interest recognized		1,074		1,008		85
Net interest foregone	$	2,958	$	2,085	$	1,690

Schedule Of Troubled Debt Restructurings [Table Text Block]

	Loans Modified as TDRs During the Year Ended December 31, 2021
	No. of Contracts		Pre-Modification Outstanding Recorded Investment		Post-Modification Outstanding Recorded Investment		Specific Reserve		Charge-offs
	(Dollars in thousands)

Commercial loans		3	$	2,150	$	2,150	$	—	$	—
Residential mortgage and equity lines		2		3		3		—		—
Total		5	$	2,153	$	2,153	$	—	$	—

	Loans Modified as TDRs During the Year Ended December 31, 2020
	No. of Contracts		Pre-Modification Outstanding Recorded Investment		Post-Modification Outstanding Recorded Investment		Specific Reserve		Charge-offs
	(Dollars in thousands)

Commercial loans		5	$	5,417	$	5,417	$	—	$	—
Total		5	$	5,417	$	5,417	$	—	$	—

	Loans Modified as TDRs During the Year Ended December 31, 2019
	No. of Contracts		Pre-Modification Outstanding Recorded Investment		Post-Modification Outstanding Recorded Investment		Specific Reserve		Charge-off
	(Dollars in thousands)

Commercial loans		23	$	25,937	$	21,874	$	2,190	$	4,063
Residential mortgage and equity lines		1		42		42		—		—
Total		24	$	25,979	$	21,916	$	2,190	$	4,063

Non Accrual Troubled Debt Restructurings [Table Text Block]

	December 31, 2021
Non-accrual TDRs	Payment Deferral		Rate Reduction		Rate Reduction and Payment Deferral		Total
	(In thousands)
Commercial loans	$	7,717	$	—	$	—	$	7,717
Residential mortgage loans		458		—		—		458
Total non-accrual TDRs	$	8,175	$	—	$	—	$	8,175

	December 31, 2020
Non-accrual TDRs	Payment Deferral		Rate Reduction		Rate Reduction and Payment Deferral		Total
	(In thousands)
Commercial loans	$	8,462	$	—	$	—	$	8,462
Residential mortgage loans		523		—		—		523
Total non-accrual TDRs	$	8,985	$	—	$	—	$	8,985

Loan Held for Investment by Loan Portfolio Segments, Internal Risk Ratings and Vintage Year [Table Text Block]

	Loans Amortized Cost Basis by Origination Year
December 31, 2021	2021		2020			2019			2018			2017		Prior			Revolving Loans			Revolving Converted to Term Loans			Total
	(In thousands)
Commercial loans
Pass/Watch	$	606,770	$	268,756		$	183,468		$	142,419		$	80,701	$	100,496		$	1,437,463		$	7,433		$	2,827,506
Special Mention		395		780			1,138			1,645			3,157		—			40,761			49			47,925
Substandard		450		5,879			22,513			16,423			14,309		5,221			34,713			5,716			105,224
Doubtful		—		—			—			—			—		—			900			—			900
Total	$	607,615	$	275,415		$	207,119		$	160,487		$	98,167	$	105,717		$	1,513,837		$	13,198		$	2,981,555

YTD period charge-offs	$	—	$	1,478		$	507		$	366				$	50		$	17,650		$	—		$	20,051
YTD period recoveries		—		(1	)		(29	)		(124	)				(191	)		(1,361	)		—			(1,706	)
Net	$	—	$	1,477		$	478		$	242		$	—	$	(141	)	$	16,289		$	—		$	18,345

Real estate construction loans
Pass/Watch	$	199,188	$	188,782		$	125,316		$	24,548		$	—	$	—		$	—		$	—		$	537,834
Special Mention		—		23,107			27,672			17,374			—		—			—			—			68,153
Substandard		—		—			1,919			—			—		—			—			—			1,919
Total	$	199,188	$	211,889		$	154,907		$	41,922		$	—	$	—		$	—		$	—		$	607,906

YTD period charge-offs	$	—	$	—		$	—		$	—		$	—	$	—		$	—		$	—		$	—
YTD period recoveries		—		—			—			—			—		(76	)		—			—			(76	)
Net	$	—	$	—		$	—		$	—		$	—	$	(76	)	$	—		$	—		$	(76	)

Commercial mortgage loans
Pass/Watch	$	1,893,807	$	1,201,825		$	1,253,548		$	1,031,191		$	727,916	$	1,313,882		$	198,869		$	—		$	7,621,038
Special Mention		45,719		59,182			49,796			103,101			61,105		60,448			750			—			380,101
Substandard		1,110		—			13,483			42,803			1,580		76,906			3,297			—			139,179
Total	$	1,940,636	$	1,261,007		$	1,316,827		$	1,177,095		$	790,601	$	1,451,236		$	202,916		$	—		$	8,140,318

YTD period charge-offs	$	—	$	—		$	—		$	—		$	—	$	—		$	—		$	—		$	—
YTD period recoveries		—		—			(240	)		—			—		(28	)		(111	)		—			(379	)
Net	$	—	$	—		$	(240	)	$	—		$	—	$	(28	)	$	(111	)	$	—		$	(379	)
Residential mortgage loans
Pass/Watch	$	978,375	$	622,999		$	678,775		$	502,325		$	453,992	$	929,846		$	—		$	—		$	4,166,312
Special Mention		—		46			1,576			1,064			836		438			—			—			3,960
Substandard		1,684		147			2,698			2,574			862		5,255			—			—			13,220
Total	$	980,059	$	623,192		$	683,049		$	505,963		$	455,690	$	935,539		$	—		$	—		$	4,183,492

YTD period charge-offs	$	—	$	—		$	—		$	—		$	3	$	—		$	—					$	3
YTD period recoveries		—		—			—			—			—		(208	)		—						(208	)
Net	$	—	$	—		$	—		$	—		$	3	$	(208	)	$	—		$	—		$	(205	)

Equity lines
Pass/Watch	$	—	$	—		$	—		$	—		$	—	$	5		$	389,069		$	30,025		$	419,099
Substandard		—		—			—			—			—		—			1,230			273			1,503
Total	$	—	$	—		$	—		$	—		$	—	$	5		$	390,299		$	30,298		$	420,602

YTD period charge-offs	$	—	$	—		$	—		$	—		$	—	$	—		$	—		$	—		$	—
YTD period recoveries		—		—			—			—			—		—			(10	)		(64	)		(74	)
Net	$	—	$	—		$	—		$	—		$	—	$	—		$	(10	)	$	(64	)	$	(74	)

Installment and other loans
Pass/Watch	$	4,117	$	168		$	—		$	—		$	—	$	—		$	—		$	—		$	4,285
Total	$	4,117	$	168		$	—		$	—		$	—	$	—		$	—		$	—		$	4,285

YTD period charge-offs	$	—	$	—		$	—		$	—		$	—	$	—		$	—		$	—		$	—
YTD period recoveries		—		—			—			—			—		—			—			—			—
Net	$	—	$	—		$	—		$	—		$	—	$	—		$	—		$	—		$	—
Total loans	$	3,731,615	$	2,371,671		$	2,361,902		$	1,885,467		$	1,344,458	$	2,492,497		$	2,107,052		$	43,496		$	16,338,158
Net charge-offs/(recoveries)	$	—	$	1,477		$	238		$	242		$	3	$	(453	)	$	16,168		$	(64	)	$	17,611

Financing Receivable, Current, Allowance for Credit Loss [Table Text Block]

	For the year ended December 31,
	2021			2020			2019
Allowance for Loan Losses:	(In thousands)
Balance at beginning of year	$	166,538		$	123,224		$	122,391
Impact of ASU 2016-13 adoption		(1,560	)		—			—
Provision/(reversal) for credit losses		(11,210	)		57,500			(7,000	)
Loans charged off		(20,054	)		(21,996	)		(6,997	)
Recoveries of charged off loans		2,443			7,810			14,830
Balance at end of year	$	136,157		$	166,538		$	123,224

Reserve for Off-balance Sheet Credit Commitments:
Balance at beginning of year	$	5,880		$	3,855		$	2,250
Impact of ASU 2016-13 adoption		6,018			—			—
Provision/(reversal) for credit losses and transfers		(4,798	)		2,025			1,605
Balance at end of year	$	7,100		$	5,880		$	3,855

Notes Tables