Capital Stock (Schedule of Issued Repurchased and Outstanding Shares) (Details) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Common Stock, Shares Outstanding [Roll Forward]
Beginning balance, Shares Issued (in shares)	2,805,961,317	2,805,961,317	2,805,961,317
Beginning balance, Shares Repurchased (in shares)	(904,702,125)	(862,689,093)	(845,901,836)
Beginning balance, Shares Outstanding (in shares)	1,901,259,192	1,943,272,224	1,960,059,481
Stock award activity (in shares)	676,727	(408,891)	(566,256)
Repurchases of common stock (in shares)	(27,878,324)	(41,604,141)	(16,221,001)
Ending balance, Shares Issued (in shares)	2,805,961,317	2,805,961,317	2,805,961,317
Ending balance, Shares Repurchased (in shares)	(931,903,722)	(904,702,125)	(862,689,093)
Ending balance, Shares Outstanding (in shares)	1,874,057,595	1,901,259,192	1,943,272,224