On January 1, 2013, we reclassified certain of our businesses to correspond with internal management reporting changes and renamed our Health and Well-Being Services segment as Healthcare Services as further described in Note 2 to the consolidated financial statements included in Item 8. - Financial Statements and Supplementary Data. Prior period segment financial information has been recast to conform to the 2013 presentation.
During the year ended December 31, 2013, we repurchased 5.8 million shares in open market transactions for $502 million and paid dividends to stockholders of $168 million.
Net income was $1.2 billion, or $7.73 per diluted common share, in 2013 compared to $1.2 billion, or $7.47 per diluted common share, in 2012. The increase in net income primarily was driven by improved operating performance across most of our major business lines, including Medicare Advantage membership growth in our Retail and Employer group segments. These increases were partially offset by benefits expense of $0.99 per diluted common share in 2013 for reserve strengthening associated with our closed-block of long-term care
Investment income totaled $375 million for 2013, a decrease of $16 million from 2012, as higher average invested balances were more than offset by lower interest rates and lower net realized capital gains year-over-year.
(3) Military services benefits payable primarily represents the run-out of the claims liability associated with our previous TRICARE South Region contract that expired on March 31, 2012. A corresponding receivable for reimbursement by the federal government is included in the military services receivable in the previous receivables table.
In addition, we operate as a holding company in a highly regulated industry. Humana Inc., our parent company, is dependent upon dividends and administrative expense reimbursements from our subsidiaries, most of which are subject to regulatory restrictions. We continue to maintain significant levels of aggregate excess statutory capital and surplus in our state-regulated insurance subsidiaries. Cash, cash equivalents, and short-term investments at the parent company were $508 million at December 31, 2013 and $346 million at December 31, 2012 reflecting higher profit contribution from non-regulated businesses. Our use of operating cash flows derived from our non-insurance subsidiaries, such as in our Healthcare Services segment, is generally not restricted by Departments of Insurance. Our subsidiaries paid dividends to the parent of $967 million in 2013, $1.2 billion in 2012, and $1.1 billion in 2011. The decline in dividends to the parent in 2013 primarily was a result of higher
Goodwill represents the unamortized excess of cost over the fair value of the net tangible and other intangible assets acquired. We are required to test at least annually for impairment at a level of reporting referred to as the reporting unit, and more frequently if adverse events or changes in circumstances indicate that the asset may be impaired. A reporting unit either is our operating segments or one level below the operating segments,
Restricted stock is granted with a fair value equal to the market price of our common stock on the date of grant and generally vests three years from the date of grant. The weighted-average grant date fair value of our restricted stock was $73.50 in 2013, $85.29 in 2012, and $67.70 in 2011. Activity for our restricted stock was as follows for the year ended December 31, 2013:
In addition, we establish reserves for future policy benefits in recognition of the fact that some of the premium received in the earlier years is intended to pay anticipated benefits to be incurred in future years. At policy issuance, these reserves are recognized on a net level premium method based on interest rates, mortality, morbidity, and maintenance expense assumptions. The assumptions used to determine the liability for future policy benefits are established and locked in at the time each contract is issued and only change if our expected future experience deteriorates to the point that the level of the liability, together with the present value of future gross premiums, are not adequate to provide for future expected policy benefits and maintenance costs (i.e. the loss recognition date).
During 2013, we recorded a loss for a premium deficiency. The premium deficiency was based on current and anticipated experience that had deteriorated from our locked-in assumptions from the previous December 31, 2010 loss recognition date, particularly as they related to emerging experience due to an increase in life expectancies and utilization of home health care services. Based on this deterioration, and combined with lower interest rates, we determined that our existing future policy benefits payable, together with the present value of future gross premiums, associated with our closed block of long-term care insurance policies were not adequate to provide for future policy benefits and maintenance costs under these policies; therefore we unlocked and modified our assumptions based on current expectations. Accordingly, during 2013 we recorded $243 million of additional benefits expense, with a corresponding increase in future policy benefits payable of $350 million partially offset by a related reinsurance recoverable of $107 million included in other long-term assets.