Inventories (Policies)	12 Months Ended
	Dec. 31, 2018
Inventory Disclosure [Abstract]
Inventory, Policy	InventoriesInventories are stated at the lower of cost and net realizable value. Cost represents invoice or production cost for new items and original cost. Production cost includes material, labor and manufacturing overhead. Some domestic manufacturing and field service finished products and parts inventories for drill bits, completion products and bulk materials are recorded using the last-in, first-out method. The remaining inventory is recorded on the average cost method. We regularly review inventory quantities on hand and record provisions for excess or obsolete inventory based primarily on historical usage, estimated product demand and technological developments.Inventories are stated at the lower of cost and net realizable value.