Inventories (Narrative) (Details)	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Percent of inventory valued on a LIFO basis	84.00%	87.00%

The percentage of LIFO (last in first out) inventory to total inventory as of the balance sheet date if other than 100 percent.

No definition available.

Name:	us-gaap_PercentageOfLIFOInventory
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant