Allowance for Credit Losses (ACL) - Disaggregated analysis of the changes in allowance for credit losses (Details) - USD ($)		3 Months Ended		12 Months Ended
	Mar. 01, 2022	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Allowance for credit losses
Balance at beginning of period		$ 356,444,000	$ 301,807,000	$ 301,807,000
Charge-offs		(4,627,000)	(5,490,000)	(23,446,000)
Recoveries		3,589,000	3,167,000
Net (charge-offs) recoveries		(1,038,000)	(2,323,000)
Provision (recovery)		15,239,000	(22,003,000)
Balance at end of period		370,645,000	300,396,000	356,444,000
Quantitative allowance
Collectively evaluated		341,504,000	288,316,000
Individually evaluated		16,782,000	8,431,000
Total quantitative allowance		358,286,000	296,747,000
Qualitative allowance		12,359,000	3,649,000
Unfunded Commitment
Allowance for credit losses
Provision (recovery)		17,900,000	(142,000)
Initial PCD Allowance
Allowance for credit losses
Balance at end of period			9,218,000
Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			13,697,000
Residential Mortgage Sr.
Allowance for credit losses
Balance at beginning of period		72,188,000	47,036,000	47,036,000
Charge-offs		(2,000)	(58,000)
Recoveries		294,000	394,000
Net (charge-offs) recoveries		292,000	336,000
Provision (recovery)		4,871,000	(1,806,000)
Balance at end of period		77,351,000	46,002,000	72,188,000
Quantitative allowance
Collectively evaluated		77,982,000	45,805,000
Individually evaluated		197,000	168,000
Total quantitative allowance		78,179,000	45,973,000
Qualitative allowance		(828,000)	29,000
Residential Mortgage Sr. | Initial PCD Allowance
Allowance for credit losses
Balance at end of period			84,000
Residential Mortgage Sr. | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			352,000
Residential Mortgage Jr.
Allowance for credit losses
Balance at beginning of period		405,000	611,000	611,000
Charge-offs			(19,000)
Recoveries		5,000	55,000
Net (charge-offs) recoveries		5,000	36,000
Provision (recovery)		(61,000)	(87,000)
Balance at end of period		349,000	586,000	405,000
Quantitative allowance
Collectively evaluated		350,000	586,000
Total quantitative allowance		350,000	586,000
Qualitative allowance		(1,000)
Residential Mortgage Jr. | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			26,000
HELOC
Allowance for credit losses
Balance at beginning of period		14,886,000	13,325,000	13,325,000
Charge-offs		(39,000)	(218,000)
Recoveries		245,000	257,000
Net (charge-offs) recoveries		206,000	39,000
Provision (recovery)		(774,000)	175,000
Balance at end of period		14,318,000	13,671,000	14,886,000
Quantitative allowance
Collectively evaluated		12,229,000	12,301,000
Individually evaluated		2,285,000	1,357,000
Total quantitative allowance		14,514,000	13,658,000
Qualitative allowance		(196,000)	13,000
HELOC | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			132,000
Residential Construction
Allowance for credit losses
Balance at beginning of period		8,974,000	4,997,000	4,997,000
Recoveries		72,000	3,000
Net (charge-offs) recoveries		72,000	3,000
Provision (recovery)		130,000	614,000
Balance at end of period		9,176,000	5,616,000	8,974,000
Quantitative allowance
Collectively evaluated		8,994,000	5,616,000
Total quantitative allowance		8,994,000	5,616,000
Qualitative allowance		182,000
Residential Construction | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			2,000
Other C&D
Allowance for credit losses
Balance at beginning of period		45,410,000	37,593,000	37,593,000
Charge-offs			(4,000)
Recoveries		258,000	234,000
Net (charge-offs) recoveries		258,000	230,000
Provision (recovery)		9,401,000	(14,438,000)
Balance at end of period		55,069,000	25,358,000	45,410,000
Quantitative allowance
Collectively evaluated		49,865,000	24,770,000
Individually evaluated		155,000	588,000
Total quantitative allowance		50,020,000	25,358,000
Qualitative allowance		5,049,000
Other C&D | Initial PCD Allowance
Allowance for credit losses
Balance at end of period			86,000
Other C&D | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			1,887,000
Consumer
Allowance for credit losses
Balance at beginning of period		22,767,000	23,149,000	23,149,000
Charge-offs		(2,729,000)	(2,661,000)
Recoveries		584,000	532,000
Net (charge-offs) recoveries		(2,145,000)	(2,129,000)
Provision (recovery)		2,697,000	828,000
Balance at end of period		23,319,000	21,899,000	22,767,000
Quantitative allowance
Collectively evaluated		23,319,000	21,899,000
Total quantitative allowance		23,319,000	21,899,000
Consumer | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			51,000
Multifamily
Allowance for credit losses
Balance at beginning of period		3,684,000	4,921,000	4,921,000
Provision (recovery)		1,823,000	(1,444,000)
Balance at end of period		5,507,000	3,903,000	3,684,000
Quantitative allowance
Collectively evaluated		5,369,000	3,903,000
Total quantitative allowance		5,369,000	3,903,000
Qualitative allowance		138,000
Multifamily | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			426,000
Municipal
Allowance for credit losses
Balance at beginning of period		849,000	565,000	565,000
Provision (recovery)		30,000	42,000
Balance at end of period		879,000	607,000	849,000
Quantitative allowance
Collectively evaluated		731,000	607,000
Total quantitative allowance		731,000	607,000
Qualitative allowance		148,000
CRE Owner Occupied
Allowance for credit losses
Balance at beginning of period		58,083,000	61,794,000	61,794,000
Charge-offs			(371,000)
Recoveries		293,000	314,000
Net (charge-offs) recoveries		293,000	(57,000)
Provision (recovery)		(835,000)	(16,641,000)
Balance at end of period		57,541,000	49,094,000	58,083,000
Quantitative allowance
Collectively evaluated		49,297,000	45,302,000
Individually evaluated		6,812,000	2,960,000
Total quantitative allowance		56,109,000	48,262,000
Qualitative allowance		1,432,000	832,000
CRE Owner Occupied | Initial PCD Allowance
Allowance for credit losses
Balance at end of period			1,479,000
CRE Owner Occupied | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			2,519,000
Non Owner Occupied CRE
Allowance for credit losses
Balance at beginning of period		78,485,000	79,649,000	79,649,000
Charge-offs		(51,000)
Recoveries		106,000	69,000
Net (charge-offs) recoveries		55,000	69,000
Provision (recovery)		3,933,000	13,945,000
Balance at end of period		82,473,000	96,360,000	78,485,000
Quantitative allowance
Collectively evaluated		78,013,000	95,051,000
Individually evaluated		2,721,000
Total quantitative allowance		80,734,000	95,051,000
Qualitative allowance		1,739,000	1,309,000
Non Owner Occupied CRE | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			2,697,000
C & I
Allowance for credit losses
Balance at beginning of period		50,713,000	28,167,000	28,167,000
Charge-offs		(1,806,000)	(2,159,000)
Recoveries		1,732,000	1,309,000
Net (charge-offs) recoveries		(74,000)	(850,000)
Provision (recovery)		(5,976,000)	(3,191,000)
Balance at end of period		44,663,000	37,300,000	$ 50,713,000
Quantitative allowance
Collectively evaluated		35,355,000	32,476,000
Individually evaluated		4,612,000	3,358,000
Total quantitative allowance		39,967,000	35,834,000
Qualitative allowance		$ 4,696,000	1,466,000
C & I | Initial PCD Allowance
Allowance for credit losses
Balance at end of period			7,569,000
C & I | Initial Non PCD Allowance
Allowance for credit losses
Balance at end of period			5,605,000
Atlantic Capital
Allowance for credit losses
Charge-offs	$ (22,100,000)
Atlantic Capital | Unfunded Commitment
Allowance for credit losses
Provision (recovery)			$ 3,400,000