Insurance reserves are established for both short and long-duration insurance contracts. Short-duration contracts are primarily related to property and casualty insurance policies where the reserving process is based on actuarial estimates of the amount of loss, including amounts for known and unknown claims. Long-duration contracts are primarily related to long term care policies and are estimated using actuarial estimates about morbidity and persistency as well as assumptions about expected investment returns and future premium rate increases. The reserve for unearned premiums represents the portion of premiums written related to the unexpired terms of coverage. The reserving process is discussed in further detail in the Reserves-Estimates and Uncertainties section below.
Future policy benefit reserves for our long term care policies are based on certain assumptions, including morbidity, persistency, inclusive of mortality, discount rates and future premium rate increases. The adequacy of the reserves is contingent upon actual experience and our future expectations related to these key assumptions. If actual or expected future experience differs from these assumptions, the reserves may not be adequate, requiring us to add to reserves.
Future policy benefit reserves represent the active life reserves related to our long term care policies which are the present value of expected future benefit payments and expenses less expected future premium. The determination of these reserves requires management to make estimates and assumptions about expected investment and policyholder experience over the life of the contract. Since many of these contracts may be in force for several decades, these assumptions are subject to significant estimation risk.
The following table includes the consolidated results of our operations including our financial measure, Core income (loss). For more detailed components of our business operations and a discussion of the Core income (loss) financial measure, see the segment sections within this MD&A. For further discussion of Net investment income and Net investment gains or losses, see the Investments section of this MD&A.
Core income increased $134 million in 2019 as compared with 2018. Core income for our Property & Casualty Operations increased approximately $223 million primarily due to higher net investment income driven by limited partnership and common stock returns and favorable current accident year underwriting results partially offset by lower favorable net prior period loss reserve development in the current year. Core results for our Life & Group segment decreased $152 million driven by a $170 million charge related to recognition of a premium deficiency as a result of the third quarter 2019 GPV. Core loss for our Corporate & Other segment improved approximately $63 million driven by lower adverse prior year A&EP reserve development.
Changes in estimates of claim and claim adjustment expense reserves, net of reinsurance, for prior years are defined as net prior year loss reserve development within this MD&A. These changes can be favorable or unfavorable. Net prior year loss reserve development does not include the effect of related acquisition expenses. Further information on our reserves is provided in Note E to the Consolidated Financial Statements included under Item 8.
Core loss improved $63 million in 2019 as compared with 2018 driven by lower adverse net prior year reserve development recorded in 2019 for A&EP under the Loss Portfolio Transfer (LPT). The LPT is further discussed in Note E to the Consolidated Financial Statements included under Item 8. Additionally, 2018 included $27 million of non-recurring costs associated with the transition to a new IT infrastructure service provider.
For the year ended December 31, 2019, $66 million of gains were recognized in Net investment gains (losses) due to the change in fair value of non-redeemable preferred stock still held as of December 31, 2019. For the year ended December 31, 2018, $73 million of losses were recognized in Net investment gains (losses) due to the change in fair value of non-redeemable preferred stock still held as of December 31, 2018. Net investment gains (losses) for the year ended December 31, 2019 included a $21 million loss related to the redemption of the Company's $500 million senior notes due August 2020. Net investment gains (losses) for the year ended December 31, 2017 included a $42 million loss related to the redemption of the Company's $350 million senior notes due November 2019.
For 2017 through 2019, the Internal Revenue Service (IRS) has accepted Loews and the Company into the Compliance Assurance Process (CAP), which is a voluntary program for large corporations. Under CAP, the IRS conducts a real-time audit and works contemporaneously with the Company to resolve any issues prior to the filing of the tax return. The Company believes that this approach should reduce tax-related uncertainties, if any.
Unfavorable development in medical professional liability was primarily due to higher than expected severity in accident years 2016 through 2018 in our aging services business, higher than expected severity in accident year 2013 in our allied healthcare business, unfavorable outcomes on individual claims and higher than expected severity in accident year 2017 in our dentists business.
Favorable development in other professional liability and management liability was primarily due to lower than expected claim frequency and favorable outcomes on individual claims in accident years 2017 and prior related to financial institutions, lower than expected large claim losses in recent accident years in our public company directors and officers liability (D&O) business and lower than expected loss adjustment expenses across accident years 2010 through 2018.
The Company's largest recoverables from a single reinsurer as of December 31, 2019, including ceded unearned premium reserves, were approximately $2.0 billion from subsidiaries of Berkshire Hathaway Insurance Group, $289 million from the Palo Verde Insurance Company and $226 million from a subsidiary of Wilton Re. These amounts are substantially collateralized. The recoverable from subsidiaries of the Berkshire Hathaway Insurance Group includes amounts related to third-party reinsurance for which NICO has assumed the credit risk under the terms of the LPT as discussed in Note E to the Consolidated Financial Statements.
The following table presents the weighted average remaining lease term for operating leases and weighted average discount rate used in calculating operating lease right-of-use assets.
For the years ended December 31, 2019 and 2018, capitalized commission costs were $2.8 billion and $2.5 billion and capitalized administrator service costs were $31 million and $24 million. For the years ended December 31, 2019 and 2018, the amount of amortization of capitalized costs were $813 million and $673 million and there were no impairment losses related to the costs capitalized. There were no adjustments to deferred costs recorded for the years ended December 31, 2019 and 2018.
We compared our prior year estimates of expected incurred losses to actual experience during the most recent year to identify potential bias in the Company’s determination of P&C claim and claim adjustment expense reserves.