The manner in which impairment losses on fixed maturity securities, available for sale, are recognized in the financial statements is dependent on the facts and circumstances related to the specific security. If we intend to sell a security or it is more likely than not that we would be required to sell a security before the recovery of its amortized cost, the security is other-than-temporarily impaired and the full amount of the impairment is recognized as a loss through earnings. If we do not expect
Our fixed maturity investments are generally purchased in the context of long-term strategies, including funding insurance liabilities, so we do not generally seek to generate short-term realized gains through the purchase and sale of such securities. In certain circumstances, including those in which securities are selling at prices which exceed our view of their underlying economic value, or when it is possible to reinvest the proceeds to better meet our long-term asset-liability objectives, we may sell certain securities. During 2018, we sold $1,295.8 million of fixed maturity investments which resulted in gross investment losses (before income taxes) of $65.8 million.
Other operating costs and expenses in our Bankers Life segment were $419.8 million in 2018, down .2 percent from 2017, and were $420.5 million in 2017, up 5.1 percent from 2016. Such expenses in 2017 include $3.5 million for estimated future state guaranty association assessments, net of premium tax offsets, related to the liquidation of Penn Treaty Network America Insurance Company ("Penn Treaty"). Other operating costs and expenses include the following (dollars in millions):
(such as non-cancelable or guaranteed renewable contracts) and require the performance of various functions and services (including insurance protection) for an extended period of time. The net cash flows from long-term care products generally cause an accumulation of amounts in the early years of a policy (accounted for as reserve increases) that will be paid out as benefits in later policy years (accounted for as reserve decreases). Accordingly, as the policies age, the benefit ratio will typically increase, but the increase in benefits will be partially offset by the imputed interest income earned on the accumulated assets. The interest-adjusted benefit ratio reflects the effects of such interest income offset (which is equal to the tabular interest on the related insurance liabilities). Since interest income is an important factor in measuring the performance of these products, management believes a benefit ratio that includes the effect of interest income is useful in analyzing product performance. We utilize the interest-adjusted benefit ratio in measuring segment performance because we believe that this performance measure is a better indicator of the ongoing businesses and trends in the business. However, the "interest-adjusted benefit ratio" does not replace the "benefit ratio" as a measure of current period benefits to current period insurance policy income. Accordingly, management reviews both "benefit ratios" and "interest-adjusted benefit ratios" when analyzing the financial results attributable to these products. The imputed investment income earned on the accumulated assets backing the long-term care reserves was $153.9 million, $198.8 million and $180.8 million in 2018, 2017 and 2016, respectively.
The following table provides the carrying value and estimated fair value of our outstanding commercial mortgage loans and the underlying collateral as of December 31, 2018 (dollars in millions):
Changes in our consolidated balance sheet between December 31, 2018 and December 31, 2017, primarily reflect: (i) our net loss for 2018; (ii) changes in the fair value of our fixed maturity securities, available for sale; (iii) completion of a long-term care reinsurance transaction in September 2018, as further described in the note to the consolidated financial statements entitled "Summary of Significant Accounting Policies - Reinsurance"; and (iv) payments to repurchase common stock of $100.9 million.
Accumulated other comprehensive income is primarily comprised of the net effect of unrealized appreciation (depreciation) on our investments. These amounts, included in shareholders' equity as of December 31, 2018 and 2017, were as follows (dollars in millions):
During 2016, the $95.2 million of realized losses on sales of $790.2 million of fixed maturity securities, available for sale, included: (i) $79.2 million related to various corporate securities (including $63.5 million related to sales of investments in the energy sector); (ii) $5.8 million related to commercial mortgage-backed securities; (iii) $5.7 million related to asset-backed securities; and (iv) $4.5 million related to various other investments.
During 2016, we recognized $32.3 million of impairment losses recorded in earnings which included: (i) $9.3 million of writedowns on fixed maturities in the energy sector; (ii) $3.7 million of writedowns on a direct loan due to borrower specific events; (iii) $12.7 million of writedowns on a privately placed preferred stock of an entity formed to construct and operate a chemical plant; (iv) $1.2 million of writedowns of investments held by VIEs due to other-than-temporary declines in value; and (v) $5.4 million of losses on other investments. Factors considered in determining the writedowns of investments in 2016 included the subordination status of each investment, the impact of recent downgrades and issuer specific events, including the impact of low oil prices on issuers in the energy sector.
The following table sets forth the amortized cost and estimated fair value of those fixed maturities, available for sale, with unrealized losses at December 31, 2018, by contractual maturity. Actual maturities will differ from contractual maturities because borrowers may have the right to call or prepay obligations with or without penalties. Structured securities frequently include provisions for periodic principal payments and permit periodic unscheduled payments.
At December 31, 2018, the mortgage loan balance was primarily comprised of commercial mortgage loans. Approximately 13 percent, 10 percent, 8 percent and 6 percent of the commercial mortgage loan balance were on properties located in California, Texas, Maryland and North Carolina, respectively. No other state comprised greater than five percent of the commercial mortgage loan balance. At December 31, 2018, there was one mortgage loan in process of foreclosure with a carrying value of $7.8 million. There were no other mortgage loans that were noncurrent at December 31, 2018. Our commercial mortgage loan portfolio is comprised of large commercial mortgage loans. Our loans have risk characteristics that are individually unique. Accordingly, we measure potential losses on a loan-by-loan basis rather than establishing an allowance for losses on mortgage loans. At December 31, 2018, we held residential mortgage loan investments with a carrying value of $149.6 million and a fair value of $149.1 million.
In 2010, our shareholders approved an amendment to CNO's certificate of incorporation designed to prevent certain transfers of common stock which could otherwise adversely affect our ability to use our NOLs (the "Original Section 382 Charter Amendment"). Subject to the provisions set forth in the Original Section 382 Charter Amendment, transfers of our common stock would be void and of no effect if the effect of the purported transfer would be to: (i) increase the direct or indirect ownership of our common stock by any person or public group (as such term is defined in the regulations under Section 382) from less than 5% to 5% or more of our common stock; (ii) increase the percentage of our common stock owned directly or indirectly by a person or public group owning or deemed to own 5% or more of our common stock; or (iii) create a new public group. The Original Section 382 Charter Amendment was amended and extended in 2013 and in 2016 (the "2016 Section 382 Charter Amendment"). The expiration date for the 2016 Section 382 Charter Amendment is July 31, 2019.