The medical centers we operate are primarily located in Florida and Texas, including full-service, multi-specialty medical centers staffed by primary care providers and medical specialists, urgent care facilities, and worksite medical facilities. Of the medical centers included in the table above, approximately 54 of these facilities are leased or subleased to our providers to operate.
The favorable medical claims reserve development for 2014, 2013, and 2012 primarily reflects the consistent application of trend and completion factors estimated using an assumption of moderately adverse conditions. In addition, the favorable medical claims reserve development during 2014 and 2013 reflects increased membership and better than originally expected utilization across most of our major business lines and increased financial recoveries. The increase in financial recoveries primarily resulted from claim audit process enhancements as well as increased volume of claim audits and expanded audit scope. All lines of business benefited from these improvements.
Due to the transition to the current TRICARE South Region contract on April 1, 2012, which is accounted for as an administrative services only contract as more fully described in Note 2 to the consolidated financial statements included in Item 8. - Financial Statements and Supplementary Data, there was no military services benefits payable at December 31, 2014 or 2013. This transition is also the primary reason for the decline in military services benefits expense from 2012 to 2013.
liability at December 31, 2013. Amounts charged to accumulated other comprehensive income are net of applicable deferred taxes.
making additional payments to us or require us to refund HHS a portion of the premiums we received. HHS guidance provides that risk corridor collections over the life of the three year program will first be applied to any shortfalls from previous benefit years before application to current year obligations.
Premiums revenue is estimated by multiplying the membership covered under the various contracts by the contractual rates. Premiums revenue is recognized as income in the period members are entitled to receive services, and is net of estimated uncollectible amounts, retroactive membership adjustments, and adjustments to recognize rebates under the minimum benefit ratios required under the Health Care Reform Law. We estimate policyholder rebates by projecting calendar year minimum benefit ratios for the individual, small group, and large group markets, as defined by the Health Care Reform Law using a methodology prescribed by HHS, separately by state and legal entity. Beginning in 2014, Medicare Advantage products were also subject to minimum benefit ratio requirements under the Health Care Reform Law. Estimated calendar year rebates recognized ratably during the year are revised each period to reflect current experience. Retroactive membership adjustments result from enrollment changes not yet processed, or not yet reported by an employer group or the government. We routinely monitor the collectibility of specific accounts, the aging of receivables, historical retroactivity trends, estimated rebates, as well as prevailing and anticipated economic
On April 1, 2012, we began delivering services under our current TRICARE South Region contract with the DoD. Under the current contract, we provide administrative services, including offering access to our provider networks and clinical programs, claim processing, customer service, enrollment, and other services, while the federal government retains all of the risk of the cost of health benefits. We account for revenues under the current contract net of estimated health care costs similar to an administrative services fee only agreement. The current contract includes fixed administrative services fees and incentive fees and penalties. Administrative services fees are recognized as services are performed.
Approximately 96% of our debt securities were investment-grade quality, with a weighted average credit rating of AA- by S&P at December 31, 2014. Most of the debt securities that were below investment-grade were rated BB, the higher end of the below investment-grade rating scale. At December 31, 2014, 7% of our tax-exempt municipal securities were pre-refunded, generally with U.S. government and agency securities. Tax-exempt municipal securities that were not pre-refunded were diversified among general obligation bonds of U.S. states and local municipalities as well as special revenue bonds. General obligation bonds, which are backed by the taxing power and full faith of the issuer, accounted for 36% of the tax-exempt municipals that were not pre-refunded in the portfolio. Special revenue bonds, issued by a municipality to finance a specific public works project such as utilities, water and sewer, transportation, or education, and supported by the revenues of that project, accounted for the remaining 64% of these municipals. Our general obligation bonds are diversified across the United States with no individual state exceeding 11%. In addition, 16% of our tax-exempt securities were insured by bond insurers and had an equivalent weighted average S&P credit rating of AA exclusive of the bond insurers’ guarantee. Our investment policy limits investments in a single issuer and requires diversification among various asset types.
As discussed in Note 2, we cover prescription drug benefits in accordance with Medicare Part D under multiple contracts with CMS. The consolidated balance sheets include the following amounts associated with Medicare Part D as of December 31, 2014 and 2013:
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. Principal components of our net deferred tax balances at December 31, 2014 and 2013 were as follows:
Total compensation expense not yet recognized related to nonvested options was $6 million at December 31, 2014. We expect to recognize this compensation expense over a weighted-average period of approximately 1.6 years.
In addition, CMS' comments in formalized guidance regarding “overpayments” to MA plans appear to be inconsistent with CMS' prior RADV audit guidance. These statements, contained in the preamble to CMS’ final rule release regarding Medicare Advantage and Part D prescription drug benefit program regulations for Contract Year 2015,
On December 16, 2010, an individual filed a qui tam suit captioned United States of America ex rel. Marc Osheroff v. Humana et al. in the Southern District of Florida, against us, several of our health plan subsidiaries, and certain other companies that operate medical centers in Miami-Dade County, Florida. After the U.S. government declined to intervene, the Court ordered the complaint unsealed, and the individual plaintiff amended his complaint and served the Company on December 8, 2011. The amended complaint alleged certain civil violations by our CAC Medical Centers in Florida, including offering various amenities such as transportation and meals, to Medicare and dual eligible individuals in our community center settings. The amended complaint also alleged civil violations by our Medicare Advantage health plans in Florida, arising from the alleged activities of our CAC Medical Centers and the codefendants in the complaint. The amended complaint sought damages and penalties on behalf of the United States under the Anti-Inducement and Anti-Kickback Statutes and the False Claims Act. On September 28, 2012, the Court dismissed, with prejudice, all causes of action that were asserted in the amended complaint. On November 19, 2013, the individual plaintiff appealed the dismissal of the amended complaint. On January 16, 2015, the Court of Appeals for the Eleventh Circuit affirmed the dismissal of the amended complaint.
On January 1, 2014, we reclassified certain of our businesses from our Healthcare Services segment to our Employer Group segment to correspond with internal management reporting changes. Our reportable segments remain the same and prior period segment financial information has been recast to conform to the 2014 presentation.
In addition, future policy benefits payable include amounts of $210 million at December 31, 2014 and $215 million at December 31, 2013 which are subject to 100% coinsurance agreements as more fully described in Note 19.
Future policy benefits payable include $1.5 billion at December 31, 2014 and $1.4 billion at December 31, 2013 associated with a non-strategic closed block of long-term care insurance policies acquired in connection with the 2007 acquisition of KMG. Future policy benefits payable includes amounts charged to accumulated other comprehensive income for an additional liability that would exist on our closed-block of long-term care insurance policies if unrealized gains on the sale of the investments backing such products had been realized and the proceeds reinvested at then current yields. There was $123 million of additional liability at December 31, 2014 and no additional liability at December 31, 2013. Amounts charged to accumulated other comprehensive income are net of applicable deferred taxes.