If we fail to effectively implement our operational and strategic initiatives with respect to the implementation of the Health Care Reform Law, our business may be materially adversely affected. Additionally, potential legislative changes, including activities to repeal or replace the Health Care Reform Law, creates uncertainty for our business, and we cannot predict when, or in what form, such legislative changes may occur. We may be unable to adjust our product offerings, geographic footprint, or pricing during any given year such legislative changes occur in sufficient time to mitigate any adverse effects.
Consolidated operating costs decreased $122 million, or 1.7%, from 2015 to $7.2 billion in 2016 primarily due to the completion of the sale of Concentra on June 1, 2015.
For additional information on our liquidity risk, please refer to Item 1A. - Risk Factors in this 2017 Form 10-K.
The detail of total net receivables was as follows at December 31, 2017, 2016 and 2015:
On June 1, 2015, we completed the sale of Concentra for approximately $1,055 million in cash, excluding approximately $22 million of transaction costs.
We entered into a commercial paper program in October 2014. Net repayments of commercial paper were $153 million in 2017 and the maximum principal amount outstanding at any one time during 2017 was $500 million. Net repayments of commercial paper were $2 million in 2016 and the maximum principal amount outstanding at any one time during 2016 was $475 million. Net proceeds from the issuance of commercial paper were $298 million in 2015 and the maximum principal amount outstanding at any one time during 2015 was $414 million.
We bill and collect premium from employer groups and members in our Medicare and other individual products monthly. We receive monthly premiums from the federal government and various states according to government specified payment rates and various contractual terms. Changes in revenues from for our Medicare and commercial medical products resulting from the periodic changes in risk-adjustment scores derived from medical diagnoses for our membership are recognized when the amounts become determinable and the collectibility is reasonably assured.
All issuers of securities we own that were trading at an unrealized loss at December 31, 2017 remain current on all contractual payments. After taking into account these and other factors previously described, we believe these unrealized losses primarily were caused by an increase in market interest rates in the current markets than when the securities were purchased. At December 31, 2017, we did not intend to sell the securities with an unrealized loss position in accumulated other comprehensive income, and it is not likely that we will be required to sell these securities before recovery of their amortized cost basis. As a result, we believe that the securities with an unrealized loss were not other-than-temporarily impaired at December 31, 2017. There were no material other-than-temporary impairments in 2017, 2016, or 2015.
amended, and the receipt of necessary approvals under state insurance and healthcare laws and regulations and pursuant to certain licenses of certain of Humana’s subsidiaries, and (ii) the absence of legal restraints and prohibitions on the consummation of the Merger.
The Health Care Reform Law also established risk spreading premium stabilization programs effective January 1, 2014, with an annual open enrollment period. The risk spreading programs are applicable to certain of our commercial medical insurance products. In the aggregate, our commercial medical insurance products represented approximately
Level 3 - Unobservable inputs that are supported by little or no market activity and are significant to the fair value of the assets or liabilities. Level 3 includes assets and liabilities whose value is determined using pricing models, discounted cash flow methodologies, or similar techniques reflecting our own assumptions about the assumptions market participants would use as well as those requiring significant management judgment.
In June 2016, the FASB issued guidance introducing a new model for recognizing credit losses on financial instruments based on an estimate of current expected credit losses. The guidance is effective for us beginning January 1, 2020. The new current expected credit losses (CECL) model generally calls for the immediate recognition of all expected credit losses and applies to loans, accounts and trade receivables as well as other financial assets measured at amortized cost, loan commitments and off-balance sheet credit exposures, debt securities and other financial assets measured at fair value through other comprehensive income, and beneficial interests in securitized financial assets. The new guidance replaces the current incurred loss model for measuring expected credit losses, requires expected losses on available-for-sale debt securities to be recognized through an allowance for credit losses rather than as reductions in the amortized cost of the securities, and provides for additional disclosure requirements. Our investment portfolio consists of available-for-sale debt securities. We are currently evaluating the impact on our results of operations, financial condition, or cash flows.
As part of our ongoing business, we do not participate or knowingly seek to participate in transactions that generate relationships with unconsolidated entities or financial partnerships, such as entities often referred to as structured finance or special purpose entities, or SPEs, which would have been established for the purpose of facilitating off-balance sheet arrangements or other contractually narrow or limited purposes. As of December 31, 2017, we were not involved in any SPE transactions.
Our Medicare products, which accounted for approximately 78% of our total premiums and services revenue for the year ended December 31, 2017, primarily consisted of products covered under the Medicare Advantage and Medicare Part D Prescription Drug Plan contracts with the federal government. These contracts are renewed generally for a calendar year term unless CMS notifies us of its decision not to renew by May 1 of the calendar year in which the contract would end, or we notify CMS of our decision not to renew by the first Monday in June of the calendar year in which the contract would end. All material contracts between Humana and CMS relating to our Medicare products have been renewed for 2018, and all of our product offerings filed with CMS for 2018 have been approved.
As a government contractor, we may also be subject to qui tam litigation brought by individuals who seek to sue on behalf of the government, alleging that the government contractor submitted false claims to the government including, among other allegations, those resulting from coding and review practices under the Medicare risk adjustment model. Qui tam litigation is filed under seal to allow the government an opportunity to investigate and to decide if it wishes to intervene and assume control of the litigation. If the government does not intervene, the lawsuit is unsealed, and the
used to determine future policy benefits payable as detailed in Note 2. Excluding reinsurance associated with the Health Care Reform Law discussed in Note 2, reinsurance recoverables, included in other current and long-term assets, were $824 million at December 31, 2017 and $822 million at December 31, 2016. The percentage of these reinsurance recoverables resulting from 100% coinsurance agreements was approximately 33% at December 31, 2017 and approximately 34% at December 31, 2016. Premiums ceded were $969 million in 2017, $842 million in 2016 and $821 million in 2015. Benefits ceded were $844 million in 2017, $767 million in 2016, and $666 million in 2015. Ceded premium and benefits reflect a July 1, 2014 amendment ceding all risk under a Medicaid contract to a third party reinsurer.