Capital Stock (Rollforward Of Common Stock Activity) (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Class of Stock [Line Items]
Common stock, beginning balance	448,900
Treasury stock, beginning balance	37,671
Common stock, ending balance	448,900	448,900
Treasury stock, ending balance	35,975	37,671
Issued
Class of Stock [Line Items]
Common stock, beginning balance	448,916	448,916	448,854
Issuance of stock for various plans, net	0	0	62
Repurchase of stock	0	0	0
Common stock, ending balance	448,916	448,916	448,916
Treasury
Class of Stock [Line Items]
Treasury stock, beginning balance	37,671	36,776	28,734
Issuance of stock for various plans, net	(2,577)	(2,745)	(4,230)
Repurchase of stock	881	3,640	12,272
Treasury stock, ending balance	35,975	37,671	36,776