Accounting policies (Policies)	6 Months Ended
Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Use of Estimates in the Preparation of Financial Statements	Use of Estimates in the Preparation of Financial Statements — The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. A material estimate that is particularly susceptible to significant change in the near term relates to the determination of the allowance for credit losses. Other significant estimates, which may be subject to change, include fair value determinations and disclosures, impairment of investments, goodwill, loans, as well as valuation of deferred tax assets.
Adoption of New Accounting Standard	Adoption of New Accounting Standards On January 1, 2023, the Company adopted Accounting Standard Update ("ASU") 2022-02 Financial Instruments-Credit Losses (Topic 326): Troubled Debt Restructurings ("TDR") and Vintage Disclosures. This ASU eliminates recognition and measurement guidance for TDRs by creditors in Subtopic 310-40, Receivables-Troubled Debt Restructurings by Creditors, while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty, and to require that an entity disclose current-period gross write-offs by year of origination (i.e. the vintage year) for financing receivables and net investments in leases within the scope of Subtopic 326-20, Financial Instruments-Credit Losses-Measured at Amortized Cost. For entities that have adopted ASU 2016-13, this ASU is effective for interim and reporting periods beginning after December 15, 2022. The Company adopted this ASU on a prospective basis. Results for reporting periods beginning after January 1, 2023 are presented under ASU 2022-02 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The adoption of this ASU did not have a material impact on our consolidated financial statements. In March 2023, the FASB issued ASU 2023-02 Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method, which expands the population of investments for which an investor may elect to apply the proportional amortization method. Under this ASU, an investor in a tax equity investment may elect the proportional amortization method for qualifying investments on a tax credit program-by-program basis. To qualify for the proportional amortization method, an investment must meet the criteria previously applicable to Low Income Housing Tax Credit ("LIHTC") investments, as clarified by the ASU. This ASU is effective in the first quarter of 2024. Early adoption is permitted as of an interim period with retrospective application to the beginning of the fiscal year. The Bank invests in various tax credit partnerships pursuant to Sections 42 and 48 of the Internal Revenue Code of 1986 (the “Code”). The Bank acts as a limited partner in these investments and does not exercise control over the operating or financial policies of the partnerships and as such, is not considered the primary beneficiary of the partnership. Upon entering into new solar tax equity investments in the second quarter of 2023, the Company adopted ASU 2023-02 on a prospective basis and implemented the proportional amortization method of accounting. The proportional amortization method recognizes the amortization of the cost of the investment as a component of income tax expense. In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments in this update provide temporary, optional guidance to ease the potential burden in accounting for transitioning away from reference rates such as LIBOR. The amendments provide optional expedients and exceptions for applying GAAP to transactions affected by reference rate reform if certain criteria are met. The amendments primarily include relief related to contract modifications and hedging relationships, as well as providing a one-time election for the sale or transfer of debt securities classified as held-to-maturity. This ASU was effective in June 2023. and it did not have a material impact on our consolidated financial statements. As a result of the phase out of LIBOR, our interest rate swap derivatives and the associated loans that were indexed to LIBOR, have been replaced with one month CME Term SOFR. The Bank will continue to use multiple alternative indices as replacements for LIBOR for newly originated instruments. All remaining financial instruments indexed to LIBOR have been transitioned to a replacement index, as of June 30, 2023. In March 2022, the FASB issued ASU 2022-01, Derivatives and Hedging (Topic 815): Fair Value Hedging—Portfolio Layer Method, was effective in the first quarter of 2023. The amendments in ASU 2022-01 allow nonprepayable financial assets to be included in a closed portfolio hedged using the portfolio layer method. That expanded scope permits an entity to apply the same portfolio hedging method to both prepayable and non-prepayable financial assets, thereby allowing consistent accounting for similar hedges. This ASU expanded the previous single-layer model to allow multiple hedged layers of a single closed portfolio. As a result, an entity can achieve hedge accounting for hedges of a greater proportion of the interest rate risk inherent in the assets included in the closed portfolio, further aligning hedge accounting with risk management strategies. To reflect that expansion, the last-of-layer method is renamed the portfolio layer method. This ASU also clarifies that fair value basis adjustments in an existing portfolio layer method hedge are maintained at the closed portfolio level (Balance Sheet line item level) and are therefore not allocated to individual assets. In June 2023, fair value hedging transactions were executed in which $1.0 billion notional pay-fixed interest rate swaps were consummated with maturities ranging from four to five years in which the Company pays a weighted average fixed rate of approximately 3.8% and receives daily SOFR. The fair value of these instruments totaled $11.1 million on June 30, 2023. This pay-fixed interest rate swap is designated as a partial-term fair value hedge using the Portfolio Layer Method, in accordance with ASU 2022-01. Refer to Note 10 – Derivative Financial Instruments of the notes to the unaudited condensed consolidated financial statements of this report for additional information.

Accounting policies (Policies)

6 Months Ended

Jun. 30, 2023

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Use of Estimates in the Preparation of Financial Statements

Use of Estimates in the Preparation of Financial Statements — The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosures of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. A material estimate that is particularly susceptible to significant change in the near term relates to the determination of the allowance for credit losses. Other significant estimates, which may be subject to change, include fair value determinations and disclosures, impairment of investments, goodwill, loans, as well as valuation of deferred tax assets.

Adoption of New Accounting Standard

Adoption of New Accounting Standards

On January 1, 2023, the Company adopted Accounting Standard Update ("ASU") 2022-02 Financial Instruments-Credit Losses (Topic 326): Troubled Debt Restructurings ("TDR") and Vintage Disclosures. This ASU eliminates recognition and measurement guidance for TDRs by creditors in Subtopic 310-40, Receivables-Troubled Debt Restructurings by Creditors, while enhancing disclosure requirements for certain loan refinancings and restructurings by creditors when a borrower is experiencing financial difficulty, and to require that an entity disclose current-period gross write-offs by year of origination (i.e. the vintage year) for financing receivables and net investments in leases within the scope of Subtopic 326-20, Financial Instruments-Credit Losses-Measured at Amortized Cost. For entities that have adopted ASU 2016-13, this ASU is effective for interim and reporting periods beginning after December 15, 2022. The Company adopted this ASU on a prospective basis. Results for reporting periods beginning after January 1, 2023 are presented under ASU 2022-02 while prior period amounts continue to be reported in accordance with previously applicable GAAP. The adoption of this ASU did not have a material impact on our consolidated financial statements.

In March 2023, the FASB issued ASU 2023-02 Accounting for Investments in Tax Credit Structures Using the Proportional Amortization Method, which expands the population of investments for which an investor may elect to apply the proportional amortization method. Under this ASU, an investor in a tax equity investment may elect the proportional amortization method for qualifying investments on a tax credit program-by-program basis. To qualify for the proportional amortization method, an investment must meet the criteria previously applicable to Low Income Housing Tax Credit ("LIHTC") investments, as clarified by the ASU. This ASU is effective in the first quarter of 2024. Early adoption is permitted as of an interim period with retrospective application to the beginning of the fiscal year.

The Bank invests in various tax credit partnerships pursuant to Sections 42 and 48 of the Internal Revenue Code of 1986 (the “Code”). The Bank acts as a limited partner in these investments and does not exercise control over the operating or financial policies of the partnerships and as such, is not considered the primary beneficiary of the partnership. Upon entering into new solar tax equity investments in the second quarter of 2023, the Company adopted ASU 2023-02 on a prospective basis and implemented the proportional amortization method of accounting. The proportional amortization method recognizes the amortization of the cost of the investment as a component of income tax expense.

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform: Facilitation of the Effects of Reference Rate Reform on Financial Reporting. The amendments in this update provide temporary, optional guidance to ease the potential burden in accounting for transitioning away from reference rates such as LIBOR. The amendments provide optional expedients and exceptions for applying GAAP to transactions affected by reference rate reform if certain criteria are met. The amendments primarily include relief related to contract modifications and hedging relationships, as well as providing a one-time election for the sale or transfer of debt securities classified as held-to-maturity. This ASU was effective in June 2023. and it did not have a material impact on our consolidated financial statements. As a result of the phase out of LIBOR, our interest rate swap derivatives and the associated loans that were indexed to LIBOR, have been replaced with one month CME Term SOFR. The Bank will continue to use multiple alternative indices as replacements for LIBOR for newly originated instruments. All remaining financial instruments indexed to LIBOR have been transitioned to a replacement index, as of June 30, 2023.

In March 2022, the FASB issued ASU 2022-01, Derivatives and Hedging (Topic 815): Fair Value Hedging—Portfolio Layer Method, was effective in the first quarter of 2023. The amendments in ASU 2022-01 allow nonprepayable financial assets to be included in a closed portfolio hedged using the portfolio layer method. That expanded scope permits an entity to apply the same portfolio hedging method to both prepayable and non-prepayable financial assets, thereby allowing consistent accounting for similar hedges. This ASU expanded the previous single-layer model to allow multiple hedged layers of a single closed portfolio. As a result, an entity can achieve hedge accounting for hedges of a greater proportion of the interest rate risk inherent in the assets included in the closed portfolio, further aligning hedge accounting with risk management strategies. To reflect that expansion, the last-of-layer method is renamed the portfolio layer method. This ASU also clarifies that fair value basis adjustments in an existing portfolio layer method hedge are maintained at the closed portfolio level (Balance Sheet line item level) and are therefore not allocated to individual assets. In June 2023, fair value hedging transactions were executed in which $1.0 billion notional pay-fixed interest rate swaps were consummated with maturities ranging from four to five years in which the Company pays a weighted average fixed rate of approximately 3.8% and receives daily SOFR. The fair value of these instruments totaled $11.1 million on June 30, 2023. This pay-fixed interest rate swap is designated as a partial-term fair value hedge using the Portfolio Layer Method, in accordance with ASU 2022-01. Refer to Note 10 – Derivative Financial Instruments of the notes to the unaudited condensed consolidated financial statements of this report for additional information.