Property at December 31 In millions | Estimated Useful Lives (Years) | 2013 | 2012 | ||||||||
Land | — | $ | 907 | $ | 916 | ||||||
Land and waterway improvements | 15-25 | 1,404 | 1,377 | ||||||||
Buildings | 5-55 | 4,945 | 4,886 | ||||||||
Machinery and equipment | 3-20 | 39,971 | 39,828 | ||||||||
Utility and supply lines | 5-20 | 2,446 | 2,350 | ||||||||
Other property | 3-50 | 2,430 | 2,267 | ||||||||
Construction in progress | — | 3,011 | 2,742 | ||||||||
Total property | $ | 55,114 | $ | 54,366 | |||||||
In millions | 2013 | 2012 | 2011 | |||||||||
Depreciation expense | $ | 2,051 | $ | 2,057 | $ | 2,177 | ||||||
Manufacturing maintenance and repair costs | $ | 2,325 | $ | 2,188 | $ | 2,247 | ||||||
Capitalized interest | $ | 78 | $ | 84 | $ | 90 | ||||||