relationships with our customers and to ensure a humanitarian approach to local patient needs.

We will continue to closely monitor repayment risk and, when necessary, we will continue to adjust our allowance for doubtful accounts.

Our assessments about the recoverability of accounts receivables can result from a complex series of judgments about future events and uncertainties and can rely heavily on estimates and assumptions. For information about the risks associated with estimates and assumptions, see Notes to Consolidated Financial Statements––Note 1C. Basis of Presentation and Significant Accounting Policies: Estimates and Assumptions.

Credit Ratings

Two major corporate debt-rating organizations, Moody’s and S&P, assign ratings to our short-term and long-term debt. A security rating is not a recommendation to buy, sell or hold securities and the rating is subject to revision or withdrawal at any time by the rating organization. Each rating should be evaluated independently of any other rating.

The following table provides the current ratings assigned by these rating agencies to our commercial paper and senior unsecured non-credit- enhanced long-term debt:

Debt Capacity

We have available lines of credit and revolving credit agreements with a group of banks and other financial intermediaries. We maintain cash and cash equivalent balances and short-term investments in excess of our commercial paper and other short-term borrowings. As of December 31, 2014, we had access to $8.4 billion of lines of credit, of which $822 million expire within one year. Of these lines of credit, $8.1 billion are unused, of which our lenders have committed to loan us $7.1 billion at our request. Also, $7.0 billion of our unused lines of credit, all of which expire in 2019, may be used to support our commercial paper borrowings.

See also "Subsequent Event" above.

Global Economic Conditions––General

The global economic environment has not had, nor do we anticipate it will have, a material impact on our liquidity or capital resources. Due to our significant operating cash flows, financial assets, access to capital markets and available lines of credit and revolving credit agreements, we continue to believe that we have, and will maintain, the ability to meet our liquidity needs for the foreseeable future. As markets conditions change, we continue to monitor our liquidity position.

Global Economic Conditions––Venezuela Operations

Our Venezuela operations continue to operate with the U.S. dollar as the functional currency due to the hyperinflationary status of the Venezuelan economy.

On February 13, 2013, the Venezuelan government devalued its currency from a rate of 4.3 to 6.3 of Venezuelan currency to the U.S. dollar. We incurred a foreign currency loss of $80 million immediately on the devaluation as a result of remeasuring the local balance sheets, and have experienced and expect to continue to experience adverse impacts to our earnings as our revenues and expenses in Venezuela continue to be translated into U.S. dollars at the lower 6.3 rate.

In the first quarter of 2014, the Venezuelan government expanded the number of exchange mechanisms, such