Significant accounting policies (Policies)	6 Months Ended
Jun. 30, 2020
Accounting Policies [Abstract]
Basis of presentation	In the opinion of management, the accompanying unaudited interim consolidated financial statements reflect all adjustments (consisting of recurring accruals) necessary for a fair statement of results on an interim basis. The unaudited interim consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”) on a basis consistent with reporting interim financial information in accordance with instructions to Form 10-Q and Article 10 of Regulation S-X under the Securities and Exchange Act of 1934, as amended. All significant intercompany transactions and balances have been eliminated on consolidation.
Use of estimates	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 disclosure 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 and assumptions.
Recent accounting pronouncements	Issued and effective as of June 30, 2020 - Credit Losses Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments The Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) (“ASU 2016-13”) which was issued in June 2016. This ASU applies a new credit loss model (current expected credit losses, or “CECL”) for determining credit-related impairments for financial instruments measured at amortized cost (including reinsurance recoverables) and requires an entity to estimate the credit losses expected over the life of an exposure or pool of exposures. The estimate of expected credit losses should consider historical information, current information, as well as reasonable and supportable forecasts, including estimates of prepayments. The expected credit losses, and subsequent adjustments to such losses, are recorded through an allowance account that is deducted from the amortized cost basis of the financial asset, with the net carrying value of the financial asset presented on the Company’s consolidated balance sheet. This ASU also amends the previous other-than-temporary impairment model for available for sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limiting the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists. The Company adopted this ASU as of January 1, 2020. For available for sale debt securities, the updated guidance was applied prospectively. For financial instruments measured at amortized cost, the updated guidance was applied by recognizing a cumulative effect adjustment of $0.4 million, net of tax, to the opening balance of retained earnings as of January 1, 2020, the beginning of the period of adoption. This adjustment is associated with “premiums receivable” and “reinsurance recoverables on unpaid and paid losses and loss adjustment expenses” in the Company’s consolidated balance sheets. The cumulative effect of the adjustment decreased retained earnings as of January 1, 2020 and increased the allowance for estimated uncollectible reinsurance. The following accounting policies have been updated to reflect the Company’s adoption of ASU 2016-13, as described above. Results for the reporting periods beginning January 1, 2020 and thereafter are presented under ASC 326, while prior period amounts continue to be reported in accordance with previous applicable GAAP. Investment Impairments The Company conducts a periodic review to identify and evaluate invested assets that may have credit impairments. Credit Impairments of Available For Sale Fixed Maturities The Company derives estimated credit losses for fixed maturities by comparing expected future cash flows to be collected to the amortized cost of the security. Estimates of expected future cash flows consider among other things, macroeconomic conditions as well as the financial condition of the issuer, near-term and long-term prospects for the issuer, and the likelihood of the recoverability of principal and interest. Beginning on January 1, 2020, credit losses are recognized through an allowance account subject to reversal, rather than a reduction in amortized cost. Declines in value attributable to factors other than credit are reported in other comprehensive income while the allowance for credit loss is charged to “realized and unrealized gains (losses) on investments” in the Company’s consolidated statements of income (loss). For fixed maturity investments the Company intends to sell or for which it is more likely than not that the Company will be required to sell before an anticipated recovery in value, the full amount of the impairment is included in “realized and unrealized gains (losses) on investments” on the Company’s consolidated statements of income (loss). The new cost basis of the investment is the previous amortized cost basis less the impairment recognized in “realized and unrealized gains (losses) on investments.” The new cost basis is not adjusted for any subsequent recoveries in fair value. The Company reports accrued investment income separately from available for sale fixed maturities, and has elected not to measure an allowance for credit losses for accrued investment income. Uncollectible accrued interest is written off when the Company determines that no additional interest payments will be received. Reinsurance Recoverables In the normal course of business, the Company’s subsidiaries cede a portion of their premium and losses through pro rata and excess of loss reinsurance agreements on a treaty or facultative basis. Reinsurance recoverables are recorded as assets, predicated on the reinsurers’ ability to meet their obligations under the reinsurance agreements. In certain instances, the Company obtains collateral, including letters of credit and trust accounts, to further reduce the credit exposure on its reinsurance recoverables. The Company reports its reinsurance recoverables net of an allowance for expected credit loss in the Company’s consolidated balance sheets. The allowance is based upon the Company’s ongoing review of amounts outstanding, the financial condition of its reinsurers, amounts and form of collateral obtained and other relevant factors. A ratings based probability-of-default and loss-given-default methodology is used to estimate the allowance for expected credit loss. Any allowance for credit losses is charged to the Company’s consolidated statements of income (loss) in the period the recoverable is recorded and revised in subsequent periods to reflect changes in the Company’s estimate of expected credit losses. Premiums receivable and unearned premium reserves Premiums are recognized as revenues pro rata over the policy period. Unearned premium reserves represent the unexpired portion of policy premiums. Accrued retrospective premiums are included in premiums receivable balances. Premiums receivable balances are reported net of an allowance for expected credit losses. The Company monitors credit risk associated with premiums receivable through its ongoing review of amounts outstanding, aging of the receivable, historical loss data and counterparty financial strength measures. The allowance also includes estimated uncollectible amounts related to dispute risk. Amounts deemed to be uncollectible, are written off against the allowance. In certain instances, credit risk may be reduced by the Company’s right to offset loss obligations or unearned premiums against premiums receivable. Any allowance for credit losses is charged to the Company’s consolidated statements of income (loss) in the period the receivable is recorded and revised in subsequent periods to reflect changes in the Company’s estimate of expected credit losses. Issued and effective as of June 30, 2020 In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements (“ASU 2018-13”). ASU 2018-13 modifies the disclosure requirements on fair value measurements. This ASU was adopted on January 1, 2020, and the Company considers the impact to be immaterial to the Company’s consolidated financial statements and disclosures. In March 2020, the FASB issued ASU 2020-03, Codification Improvements (“ASU 2020-03”), which provides updates to a wide variety of Topics in the Codification. For public business entities, this ASU was effective upon issuance. This ASU was adopted upon issuance, and did not have a material impact on the Company’s consolidated financial statements. In April 2019, the FASB issued ASU 2019-04, which identified and clarified issues relevant to ASU 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities (“ASU 2017-12”). For amendments related to ASU 2017-12, the effective date is as of the beginning of the first annual reporting period beginning after April 25, 2019. This ASU was adopted on January 1, 2020 and did not have a material impact on the Company’s consolidated financial statements. Recently issued accounting standards not yet adopted In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”). This ASU provides practical expedients and exceptions for applying GAAP to contracts and transactions affected by reference rate reform if such contracts or transactions reference LIBOR or another reference rate expected to be discontinued. Amendments in this ASU for contract modifications may be applied as of March 12, 2020 through December 31, 2022. Once adopted, this ASU must be applied prospectively for all eligible contract modifications. The Company is currently assessing the impact the implementation of this ASU will have on its consolidated financial statements and disclosures, but does not believe that such impact will be material. For additional information regarding accounting standards that the Company has not yet adopted, see Note 2, “Basis of presentation and significant accounting policies” in the Company’s audited consolidated financial statements in Part II, Item 8 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.

Issued and effective as of June 30, 2020 - Credit Losses

Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments

The Company adopted ASU 2016-13, Financial Instruments - Credit Losses (Topic 326) (“ASU 2016-13”) which was issued in June 2016. This ASU applies a new credit loss model (current expected credit losses, or “CECL”) for determining credit-related impairments for financial instruments measured at amortized cost (including reinsurance recoverables) and requires an entity to estimate the credit losses expected over the life of an exposure or pool of exposures. The estimate of expected credit losses should consider historical information, current information, as well as reasonable and supportable forecasts, including estimates of prepayments. The expected credit losses, and subsequent adjustments to such losses, are recorded through an allowance account that is deducted from the amortized cost basis of the financial asset, with the net carrying value of the financial asset presented on the Company’s consolidated balance sheet.

This ASU also amends the previous other-than-temporary impairment model for available for sale debt securities by requiring the recognition of impairments relating to credit losses through an allowance account and limiting the amount of credit loss to the difference between a security’s amortized cost basis and its fair value. In addition, the length of time a security has been in an unrealized loss position will no longer impact the determination of whether a credit loss exists.

The Company adopted this ASU as of January 1, 2020. For available for sale debt securities, the updated guidance was applied prospectively. For financial instruments measured at amortized cost, the updated guidance was applied by recognizing a cumulative effect adjustment of $0.4 million, net of tax, to the opening balance of retained earnings as of January 1, 2020, the beginning of the period of adoption. This adjustment is associated with “premiums receivable” and “reinsurance recoverables on unpaid and paid losses and loss adjustment expenses” in the Company’s consolidated balance sheets. The cumulative effect of the adjustment decreased retained earnings as of January 1, 2020 and increased the allowance for estimated uncollectible reinsurance.

The following accounting policies have been updated to reflect the Company’s adoption of ASU 2016-13, as described above. Results for the reporting periods beginning January 1, 2020 and thereafter are presented under ASC 326, while prior period amounts continue to be reported in accordance with previous applicable GAAP.

Investment Impairments

The Company conducts a periodic review to identify and evaluate invested assets that may have credit impairments.

Credit Impairments of Available For Sale Fixed Maturities

The Company derives estimated credit losses for fixed maturities by comparing expected future cash flows to be collected to the amortized cost of the security. Estimates of expected future cash flows consider among other things, macroeconomic conditions as well as the financial condition of the issuer, near-term and long-term prospects for the issuer, and the likelihood of the recoverability of principal and interest.

Beginning on January 1, 2020, credit losses are recognized through an allowance account subject to reversal, rather than a reduction in amortized cost. Declines in value attributable to factors other than credit are reported in other comprehensive income while the allowance for credit loss is charged to “realized and unrealized gains (losses) on investments” in the Company’s consolidated statements of income (loss).

For fixed maturity investments the Company intends to sell or for which it is more likely than not that the Company will be required to sell before an anticipated recovery in value, the full amount of the impairment is included in “realized and unrealized gains (losses) on investments” on the Company’s consolidated statements of income (loss). The new cost basis of the investment is the previous amortized cost basis less the impairment recognized in “realized and unrealized gains (losses) on investments.” The new cost basis is not adjusted for any subsequent recoveries in fair value.

The Company reports accrued investment income separately from available for sale fixed maturities, and has elected not to measure an allowance for credit losses for accrued investment income. Uncollectible accrued interest is written off when the Company determines that no additional interest payments will be received.

Reinsurance Recoverables

In the normal course of business, the Company’s subsidiaries cede a portion of their premium and losses through pro rata and excess of loss reinsurance agreements on a treaty or facultative basis. Reinsurance recoverables are recorded as assets, predicated on the reinsurers’ ability to meet their obligations under the reinsurance agreements. In certain instances, the Company obtains collateral, including letters of credit and trust accounts, to further reduce the credit exposure on its reinsurance recoverables. The Company reports its reinsurance recoverables net of an allowance for expected credit loss in the Company’s consolidated balance sheets. The allowance is based upon the Company’s ongoing review of amounts outstanding, the financial condition of its reinsurers, amounts and form of collateral obtained and other relevant factors. A ratings based probability-of-default and loss-given-default methodology is used to estimate the allowance for expected credit loss. Any allowance for credit losses is charged to the Company’s consolidated statements of income (loss) in the period the recoverable is recorded and revised in subsequent periods to reflect changes in the Company’s estimate of expected credit losses.

Premiums receivable and unearned premium reserves

Premiums are recognized as revenues pro rata over the policy period. Unearned premium reserves represent the unexpired portion of policy premiums. Accrued retrospective premiums are included in premiums receivable balances. Premiums receivable balances are reported net of an allowance for expected credit losses. The Company monitors credit risk associated with premiums receivable through its ongoing review of amounts outstanding, aging of the receivable, historical loss data and counterparty financial strength measures. The allowance also includes estimated uncollectible amounts related to dispute risk. Amounts deemed to be uncollectible, are written off against the allowance. In certain instances, credit risk may be reduced by the Company’s right to offset loss obligations or unearned premiums against premiums receivable. Any allowance for credit losses is charged to the Company’s consolidated statements of income (loss) in the period the receivable is recorded and revised in subsequent periods to reflect changes in the Company’s estimate of expected credit losses.

Issued and effective as of June 30, 2020

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820), Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurements (“ASU 2018-13”). ASU 2018-13 modifies the disclosure requirements on fair value measurements. This ASU was adopted on January 1, 2020, and the Company considers the impact to be immaterial to the Company’s consolidated financial statements and disclosures.

In March 2020, the FASB issued ASU 2020-03, Codification Improvements (“ASU 2020-03”), which provides updates to a wide variety of Topics in the Codification. For public business entities, this ASU was effective upon issuance. This ASU was adopted upon issuance, and did not have a material impact on the Company’s consolidated financial statements.

In April 2019, the FASB issued ASU 2019-04, which identified and clarified issues relevant to ASU 2017-12, Derivatives and Hedging (Topic 815), Targeted Improvements to Accounting for Hedging Activities (“ASU 2017-12”). For amendments related to ASU 2017-12, the effective date is as of the beginning of the first annual reporting period beginning after April 25, 2019. This ASU was adopted on January 1, 2020 and did not have a material impact on the Company’s consolidated financial statements.

Recently issued accounting standards not yet adopted

In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) (“ASU 2020-04”). This ASU provides practical expedients and exceptions for applying GAAP to contracts and transactions affected by reference rate reform if such contracts or transactions reference LIBOR or another reference rate expected to be discontinued. Amendments in this ASU for contract modifications may be applied as of March 12, 2020 through December 31, 2022. Once adopted, this ASU must be applied prospectively for all eligible contract modifications. The Company is currently assessing the impact the implementation of this ASU will have on its consolidated financial statements and disclosures, but does not believe that such impact will be material.

For additional information regarding accounting standards that the Company has not yet adopted, see Note 2, “Basis of presentation and significant accounting policies” in the Company’s audited consolidated financial statements in Part II, Item 8 of the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.