amount of commitment expiration per period other commercial commitments after millions total 2012 2013 2014 2015 2016 2016 .
what percent of total commercial commitments are credit facilities?
[a] none of the credit facility was used as of december 31 , 2011 . [b] $ 100 million of the receivables securitization facility was utilized at december 31 , 2011 , which is accounted for as debt . the full program matures in august 2012 . [c] includes guaranteed obligations related to our headquarters building , equipment financings , and affiliated operations . [d] none of the letters of credit were drawn upon as of december 31 , 2011 . off-balance sheet arrangements guarantees 2013 at december 31 , 2011 , we were contingently liable for $ 325 million in guarantees . we have recorded a liability of $ 3 million for the fair value of these obligations as of december 31 , 2011 and 2010 . we entered into these contingent guarantees in the normal course of business , and they include guaranteed obligations related to our headquarters building , equipment financings , and affiliated operations . the final guarantee expires in 2022 . we are not aware of any existing event of default that would require us to satisfy these guarantees . we do not expect that these guarantees will have a material adverse effect on our consolidated financial condition , results of operations , or liquidity . other matters labor agreements 2013 in january 2010 , the nation 2019s largest freight railroads began the current round of negotiations with the labor unions . generally , contract negotiations with the various unions take place over an extended period of time . this round of negotiations was no exception . in september 2011 , the rail industry reached agreements with the united transportation union . on november 5 , 2011 , a presidential emergency board ( peb ) appointed by president obama issued recommendations to resolve the disputes between the u.s . railroads and 11 unions that had not yet reached agreements . since then , ten unions reached agreements with the railroads , all of them generally patterned on the recommendations of the peb , and the unions subsequently ratified these agreements . the railroad industry reached a tentative agreement with the brotherhood of maintenance of way employees ( bmwe ) on february 2 , 2012 , eliminating the immediate threat of a national rail strike . the bmwe now will commence ratification of this tentative agreement by its members . inflation 2013 long periods of inflation significantly increase asset replacement costs for capital-intensive companies . as a result , assuming that we replace all operating assets at current price levels , depreciation charges ( on an inflation-adjusted basis ) would be substantially greater than historically reported amounts . derivative financial instruments 2013 we may use derivative financial instruments in limited instances to assist in managing our overall exposure to fluctuations in interest rates and fuel prices . we are not a party to leveraged derivatives and , by policy , do not use derivative financial instruments for speculative purposes . derivative financial instruments qualifying for hedge accounting must maintain a specified level of effectiveness between the hedging instrument and the item being hedged , both at inception and throughout the hedged period . we formally document the nature and relationships between the hedging instruments and hedged items at inception , as well as our risk-management objectives , strategies for undertaking the various hedge transactions , and method of assessing hedge effectiveness . changes in the fair market value of derivative financial instruments that do not qualify for hedge accounting are charged to earnings . we may use swaps , collars , futures , and/or forward contracts to mitigate the risk of adverse movements in interest rates and fuel prices ; however , the use of these derivative financial instruments may limit future benefits from favorable price movements. .