debt maturities 2013 the following table presents aggregate debt maturities as of december 31 , 2007 , excluding market value adjustments . millions of dollars .
what percentage of total debt is due after 2012?
at december 31 , 2007 , we reclassified as long-term debt approximately $ 550 million of debt due within one year that we intend to refinance . this reclassification reflected our ability and intent to refinance any short- term borrowings and certain current maturities of long-term debt on a long-term basis . at december 31 , 2006 , we did not reclassify any short-term debt as long-term debt as we did not intend to refinance at that mortgaged properties 2013 equipment with a carrying value of approximately $ 2.8 billion at both december 31 , 2007 and 2006 serves as collateral for capital leases and other types of equipment obligations in accordance with the secured financing arrangements utilized to acquire such railroad equipment . as a result of the merger of missouri pacific railroad company ( mprr ) with and into uprr on january 1 , 1997 , and pursuant to the underlying indentures for the mprr mortgage bonds , uprr must maintain the same value of assets after the merger in order to comply with the security requirements of the mortgage bonds . as of the merger date , the value of the mprr assets that secured the mortgage bonds was approximately $ 6.0 billion . in accordance with the terms of the indentures , this collateral value must be maintained during the entire term of the mortgage bonds irrespective of the outstanding balance of such bonds . credit facilities 2013 on december 31 , 2007 , $ 1.9 billion of credit was available under our revolving credit facility ( the facility ) , which we entered into on april 20 , 2007 . the facility is designated for general corporate purposes and supports the issuance of commercial paper . we did not draw on the facility during 2007 . commitment fees and interest rates payable under the facility are similar to fees and rates available to comparably rated , investment-grade borrowers . the facility allows for borrowings at floating rates based on london interbank offered rates , plus a spread , depending upon our senior unsecured debt ratings . the facility requires the maintenance of a debt to net worth coverage ratio . at december 31 , 2007 , we were in compliance with this covenant . the facility does not include any other financial restrictions , credit rating triggers ( other than rating-dependent pricing ) , or any other provision that could require us to post collateral . the facility , which expires in april 2012 , replaced two $ 1 billion , 5-year facilities with terms ending in march 2009 and march 2010 . the facility includes terms that are comparable with those of the prior facilities , although the minimum net worth requirement of $ 7.5 billion in prior facilities was removed , and the facility includes a change-of-control provision . in addition to our revolving credit facility , a $ 75 million uncommitted line of credit was available . the line of credit expires in april 2008 , and was not used in 2007 . we must have equivalent credit available under our five-year facility to draw on this $ 75 million line . dividend restrictions 2013 our revolving credit facility includes a debt-to-net worth covenant that , under certain circumstances , would restrict the payment of cash dividends to our shareholders . the amount of retained earnings available for dividends was $ 11.5 billion and $ 7.8 billion at december 31 , 2007 and december 31 , 2006 , respectively . this facility replaced two credit facilities that had minimum net worth covenants that were more restrictive with respect to the amount of retained earnings available for dividends at december 31 , 2006. .