Medicaid HMO patients in Greater Orlando, Florida with a footprint that includes clinics located in Lake, Orange, Osceola and Seminole counties.
We continued to invest in our Healthcare Services segment necessary to drive effective care delivery and clinical outcomes with our acquisitions of MCCI and FPG and our 40% investment in Kindred at Home.
The consolidated benefit ratio for 2018 was 83.5%, an increase of 50 basis points from 2017 primarily due to the enhanced 2018 Medicare Advantage member benefits resulting from the investment of the better than expected 2017 individual Medicare Advantage pretax earnings and a more severe flu season in the first quarter of 2018. These items were partially offset by the positive impact from the reinstatement of the health insurance industry fee in 2018, which was contemplated in the pricing and benefit design of our products and higher favorable prior-period reserve development. Favorable prior-period medical claims reserve development decreased the consolidated benefit ratio by approximately 90 basis points in both 2018 and 2017.
Individual Medicare Advantage membership increased 203,200 members, or 7.1%, from December 31, 2017 to December 31, 2018 reflecting net membership additions associated with last year's Annual Election Period, or AEP, for Medicare beneficiaries. For full year 2019, we anticipate net membership growth in our individual Medicare Advantage offerings of 375,000 to 400,000.
Group and Specialty segment services revenue increased $209 million, or 33.4%, from 2017 to 2018 as a result of the transition to the TRICARE T2017 East Region contract on January 1, 2018.
Retail segment premiums increased $1.4 billion, or 3.2%, from 2016 to 2017 primarily due to Medicare Advantage membership growth and increased per-member premiums for certain of the segment's products. Average group and individual Medicare Advantage membership increased 3.4% in 2017. Average membership is calculated by summing the ending membership for each month in a period and dividing the result by the number of months in a period. Premiums revenue reflects changes in membership and average per-member premiums. Items impacting average per-member premiums include changes in premium rates as well as changes in the geographic mix of membership, the mix of product offerings, and the mix of benefit plans selected by our membership.
Our TRICARE members are served by both in-network and out-of-network providers in accordance with our contracts. We pay health care costs related to these services to the providers and are subsequently reimbursed by the DoD for such payments. We account for the payments of the federal government’s claims and the related reimbursements under deposit accounting in our consolidated balance sheets and as a financing activity under receipts (withdrawals) from contract deposits in our consolidated statements of cash flows. For 2018, health care cost reimbursements and payments were each
Other current assets includes amounts associated with Medicare Part D as discussed above and in Note 7, rebates due from pharmaceutical manufacturers and other amounts due within one year. We accrue pharmaceutical rebates as they are earned based on contractual terms and usage of the product. The balance of pharmaceutical rebates receivable was $1.3 billion at December 31, 2018 and $1.2 billion at December 31, 2017.
Approximately 97% of our debt securities were investment-grade quality, with a weighted average credit rating of AA by S&P at December 31, 2018. Most of the debt securities that were below investment-grade were rated BB, the higher end of the below investment-grade rating scale. Tax-exempt municipal securities were diversified among general obligation bonds of states and local municipalities in the United States as well as special revenue bonds issued by municipalities to finance specific public works projects such as utilities, water and sewer, transportation, or education. Our general obligation bonds are diversified across the United States with no individual state exceeding 9%. Our investment policy limits investments in a single issuer and requires diversification among various asset types.
The table above does not include the fair value of the put and call options associated with our equity investment in Kindred at Home. See Note 3 for further information.
As disclosed in Note 3, we acquired MCCI, FPG, and other health and wellness related businesses during 2018, 2017, and 2016. The values of net tangible assets acquired and the resulting goodwill and other intangible assets were recorded at fair value using Level 3 inputs. The majority of the tangible assets acquired and liabilities assumed were recorded at their carrying values as of the respective dates of acquisition, as their carrying values approximated their fair values due to their short-term nature. The fair values of goodwill and other intangible assets acquired in these acquisitions were internally estimated primarily based on the income approach. The income approach estimates fair value based on the present value of the cash flows that the assets are expected to generate in the future. We developed internal estimates for the expected future cash flows and discount rates used in the present value calculations. Other than assets acquired and liabilities assumed in these acquisitions, there were no material assets or liabilities measured at fair value on a nonrecurring basis during 2018, 2017, or 2016.
Deferred income tax balances reflect the impact of temporary differences between the tax bases of assets or liabilities and their reported amounts in our consolidated financial statements, and are stated at enacted tax rates expected to be in effect when the reported amounts are actually recovered or settled.
December 31, 2018. At December 31, 2018, approximately 2.0 million shares of our common stock were reserved for issuance under our defined contribution retirement savings plans.
In February 2019, the Board declared a cash dividend of $0.55 per share payable on April 26, 2019 to stockholders of record on March 29, 2019.