Loans and Allowance for Credit Losses: Loans and Unfunded Credit Commitments - Recorded Investment in Loans Modified in TDRs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	$ 57,000	$ 56,000	$ 90,000
Loans modified in TDRs	96,000	61,000
Partial charge-offs on loans classified as TDRs	6,000	31,000	11,000
TDRs modified within the previous 12 months that defaulted in the period	0	1,000	48,000
Boston Private
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	33,000
Loans modified in TDRs	47,000
Payment deferrals
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	31,000	55,000	87,000
Partial forgiveness of principal
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	2,000	1,000	3,000
Interest rate reductions
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	2,000
Combination Of TDR Modifications
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	22,000
Investor dependent
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	12,000	32,000	29,000
Loans modified in TDRs	15,000	36,000
TDRs modified within the previous 12 months that defaulted in the period	0	0	11,000
Investor dependent | Early stage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	12,000	6,000	9,000
Loans modified in TDRs	12,000	7,000
Investor dependent | Growth stage
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	0	26,000	20,000
Loans modified in TDRs	3,000	29,000
TDRs modified within the previous 12 months that defaulted in the period	0	0	11,000
Cash flow dependent and innovation C&I (Commercial and Industrial) | Cash flow dependent - SLBO
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	12,000	22,000	48,000
Loans modified in TDRs	34,000	22,000
TDRs modified within the previous 12 months that defaulted in the period	0	0	37,000
Cash flow dependent and innovation C&I (Commercial and Industrial) | Innovation C&I (Commercial and Industrial)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	0	1,000	0
Loans modified in TDRs	0	1,000
Private Bank
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	4,000	0	2,000
Loans modified in TDRs	12,000	0
CRE
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	29,000	0	0
Loans modified in TDRs	33,000	0
Premium wine and other | Premium wine
Financing Receivable, Troubled Debt Restructuring [Line Items]
Loans modified in TDRs during the period	0	1,000	11,000
Loans modified in TDRs	0	2,000
TDRs modified within the previous 12 months that defaulted in the period	$ 0	$ 1,000	$ 0