Capital Stock (Narrative) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2018	Feb. 29, 2016	Jun. 30, 2015
Equity, Class of Treasury Stock [Line Items]
Shares authorized	800,000,000
Common stock stated value per share (in dollars per share)	$ 0.01
Common shares outstanding	159,700,000	168,100,000
Treasury stock, number of shares retired		165,000,000
Stock repurchased	9,200,000	8,700,000	9,700,000
Preferred stock shares authorized	2,000,000
Preferred stock stated value per share (in dollars per share)	$ 1.00
Preferred stock, shares outstanding	0
2015 Authorization
Equity, Class of Treasury Stock [Line Items]
Stock repurchased	0	0	9,000,000
2016 Authorization
Equity, Class of Treasury Stock [Line Items]
Stock repurchased	9,200,000	8,700,000	700,000
2018 Authorization
Equity, Class of Treasury Stock [Line Items]
Stock repurchased	0	0	0
Common Stock
Equity, Class of Treasury Stock [Line Items]
Treasury stock, number of shares retired			165,000,000
Stock repurchased	9,400,000
Weighted-average cost per share repurchased (in dollars per share)	$ 41.71
Treasury stock, shares, acquired from employees	200,000
Common Stock | 2015 Authorization
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase authorization value						15,000,000
Common Stock | 2016 Authorization
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase authorization value					20,000,000
Common Stock | 2018 Authorization
Equity, Class of Treasury Stock [Line Items]
Common stock repurchase authorization value				15,000,000