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Summary of Significant Accounting Policies (Tables) |  | 9 Months Ended
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Jan. 01, 2021 | Sep. 30, 2023
Accounting Policies [Abstract] |  |
Reconciliation of Impact of Adopting ASU 2018-12 on AOCI, Transition Date [Table Text Block] | At the transition date, the adoption of ASU 2018-12 had no impact on retained earnings but resulted in a decrease to accumulated other comprehensive income, net of taxes, of $15.3 million, which was comprised of the following corresponding adjustments to life and annuity benefits and deferred tax liabilities.
(dollars in thousands) | January 1, 2021
Reverse reserve deficiency adjustment related to unrealized gains on underlying investment portfolio of available-for-sale securities | $ | 119,548 |
Apply updated discount rate to the liability for future policyholder benefits | (138,865) |
Increase in life and annuity benefits | (19,317) |
Decrease in deferred tax liability | 4,057 |
Decrease in accumulated other comprehensive income, net of taxes | $ | (15,260) |
Reconciliation of Impact of Adopting ASU 2018-12 on AOCI, Previously Presented Balance Sheets [Table Text Block] |  | The impact of changes in the discount rate on the liability for future policyholder benefits following the transition date are included in other comprehensive income (loss) in the respective periods and, combined with the transition adjustment, resulted in the following cumulative changes to the Company's previously presented consolidated balance sheets.
| December 31,
(dollars in thousands) | 2022 |  | 2021
Decrease (increase) in life and annuity benefits | $ | 113,396 |  |  | $ | (19,759) |
Decrease (increase) in deferred tax liability | (23,813) |  |  | 4,149 |
Increase (decrease) in accumulated other comprehensive income (loss), net of taxes | $ | 89,583 |  |  | $ | (15,610) |
Reconciliation of Impact of Adopting ASU 2018-12 on OCI, Prior Period [Table Text Block] |  | Changes in the discount rate on the liability for future policyholder benefits also resulted in an increase, or benefit, of $25.2 million and $104.5 million to the other comprehensive loss previously presented for the quarter and nine months ended September 30, 2022, which was comprised of the following adjustments.
(dollars in thousands) | Quarter Ended September 30, 2022 |  | Nine Months Ended September 30, 2022
Reverse benefit included in change in net unrealized gains (losses) on available-for-sale-investments, net of taxes, related to reversal of previously recognized reserve deficiency adjustment | $ | — |  |  | $ | (44,682) |
Change in discount rate for life and annuity benefits, net of taxes | 25,244 |  |  | 149,135 |
Increase in other comprehensive loss, net of taxes | $ | 25,244 |  |  | $ | 104,453 |

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