Financial report context:
the railroad collected approximately $ 18.8 billion and $ 16.3 billion of receivables during the years ended december 31 , 2011 and 2010 , respectively . upri used certain of these proceeds to purchase new receivables under the facility . the costs of the receivables securitization facility include interest , which will vary based on prevailing commercial paper rates , program fees paid to banks , commercial paper issuing costs , and fees for unused commitment availability . the costs of the receivables securitization facility are included in interest expense and were $ 4 million and $ 6 million for 2011 and 2010 , respectively . prior to adoption of the new accounting standard , the costs of the receivables securitization facility were included in other income and were $ 9 million for 2009 . the investors have no recourse to the railroad 2019s other assets , except for customary warranty and indemnity claims . creditors of the railroad do not have recourse to the assets of upri . in august 2011 , the receivables securitization facility was renewed for an additional 364-day period at comparable terms and conditions . contractual obligations and commercial commitments as described in the notes to the consolidated financial statements and as referenced in the tables below , we have contractual obligations and commercial commitments that may affect our financial condition . based on our assessment of the underlying provisions and circumstances of our contractual obligations and commercial commitments , including material sources of off-balance sheet and structured finance arrangements , other than the risks that we and other similarly situated companies face with respect to the condition of the capital markets ( as described in item 1a of part ii of this report ) , there is no known trend , demand , commitment , event , or uncertainty that is reasonably likely to occur that would have a material adverse effect on our consolidated results of operations , financial condition , or liquidity . in addition , our commercial obligations , financings , and commitments are customary transactions that are similar to those of other comparable corporations , particularly within the transportation industry . the following tables identify material obligations and commitments as of december 31 , 2011 : payments due by december 31 , contractual obligations after millions total 2012 2013 2014 2015 2016 2016 other .

Financial table:
contractual obligationsmillions: debt [a]; total: $ 12516; payments due by december 31 2012: $ 538; payments due by december 31 2013: $ 852; payments due by december 31 2014: $ 887; payments due by december 31 2015: $ 615; payments due by december 31 2016: $ 652; payments due by december 31 after 2016: $ 8972; payments due by december 31 other: $ -
contractual obligationsmillions: operating leases [b]; total: 4528; payments due by december 31 2012: 525; payments due by december 31 2013: 489; payments due by december 31 2014: 415; payments due by december 31 2015: 372; payments due by december 31 2016: 347; payments due by december 31 after 2016: 2380; payments due by december 31 other: -
contractual obligationsmillions: capital lease obligations [c]; total: 2559; payments due by december 31 2012: 297; payments due by december 31 2013: 269; payments due by december 31 2014: 276; payments due by december 31 2015: 276; payments due by december 31 2016: 262; payments due by december 31 after 2016: 1179; payments due by december 31 other: -
contractual obligationsmillions: purchase obligations [d]; total: 5137; payments due by december 31 2012: 2598; payments due by december 31 2013: 568; payments due by december 31 2014: 560; payments due by december 31 2015: 276; payments due by december 31 2016: 245; payments due by december 31 after 2016: 858; payments due by december 31 other: 32
contractual obligationsmillions: other post retirement benefits [e]; total: 249; payments due by december 31 2012: 26; payments due by december 31 2013: 26; payments due by december 31 2014: 26; payments due by december 31 2015: 26; payments due by december 31 2016: 26; payments due by december 31 after 2016: 119; payments due by december 31 other: -
contractual obligationsmillions: income tax contingencies [f]; total: 107; payments due by december 31 2012: 31; payments due by december 31 2013: -; payments due by december 31 2014: -; payments due by december 31 2015: -; payments due by december 31 2016: -; payments due by december 31 after 2016: -; payments due by december 31 other: 76
contractual obligationsmillions: total contractualobligations; total: $ 25096; payments due by december 31 2012: $ 4015; payments due by december 31 2013: $ 2204; payments due by december 31 2014: $ 2164; payments due by december 31 2015: $ 1565; payments due by december 31 2016: $ 1532; payments due by december 31 after 2016: $ 13508; payments due by december 31 other: $ 108

Additional report context:
[a] excludes capital lease obligations of $ 1874 million and unamortized discount of $ 364 million . includes an interest component of $ 5120 million . [b] includes leases for locomotives , freight cars , other equipment , and real estate . [c] represents total obligations , including interest component of $ 685 million . [d] purchase obligations include locomotive maintenance contracts ; purchase commitments for fuel purchases , locomotives , ties , ballast , and rail ; and agreements to purchase other goods and services . for amounts where we cannot reasonably estimate the year of settlement , they are reflected in the other column . [e] includes estimated other post retirement , medical , and life insurance payments and payments made under the unfunded pension plan for the next ten years . no amounts are included for funded pension obligations as no contributions are currently required . [f] future cash flows for income tax contingencies reflect the recorded liability for unrecognized tax benefits , including interest and penalties , as of december 31 , 2011 . where we can reasonably estimate the years in which these liabilities may be settled , this is shown in the table . for amounts where we cannot reasonably estimate the year of settlement , they are reflected in the other column. .

Question: what percentage of total material obligations and commitments as of december 31 , 2011 are operating leases?
Answer: 18%