Inventories	12 Months Ended
Inventories	Dec. 31, 2019
Inventories [Abstract]
Inventories	Note 4—Inventories Inventories at December 31 were: Millions of Dollars 2019 2018 Crude oil and natural gas $ 472 432 Materials and supplies 554 575 $ 1,026 1,007 Inventories valued on the LIFO basis totaled $ 286 million and $ 292 million at December 31, 2019 and 2018, respectively. The estimated excess of current replacement cost over LIFO cost of inventories was approximately $ 155 million and $ 75 million at December 31, 2019 and December 31, 2018, respectively.