Capital Stock (Details) - USD ($)								3 Months Ended		9 Months Ended		12 Months Ended		48 Months Ended
	Oct. 10, 2017	Sep. 01, 2017	Jul. 12, 2017	Dec. 01, 2016	Sep. 07, 2016	Sep. 01, 2016	Jul. 12, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017	Feb. 02, 2017
Class of Stock [Line Items]
Cash dividends declared (dollars per share)			$ 0.10		$ 0.10		$ 0.07	$ 0.10	$ 0.17	$ 0.30	$ 0.31
Dividends paid (dollars per share)		$ 0.10		$ 0.10		$ 0.07							$ 0.31
Cash dividends paid										$ 75,000,000	$ 56,000,000
Payments for repurchase of stock										205,000,000	200,000,000
Scenario, Forecast
Class of Stock [Line Items]
Dividends paid (dollars per share)												$ 0.44
Common Stock
Class of Stock [Line Items]
Cash dividends paid										$ 75,000,000	$ 56,000,000
Stock repurchase program, authorized amount															$ 2,100,000,000.0
Shares repurchased (shares)								5,592,239		6,435,359				37,649,469
Average price of shares repurchased (dollars per share)								$ 31.29		$ 31.88				$ 29.71
Payments for repurchase of stock								$ 175,000,000		$ 205,000,000				$ 1,118,000,000
Common Stock | Payments for Share Repurchases Related to Employee Stock Based Compensation
Class of Stock [Line Items]
Shares repurchased (shares)										0
Common Stock | Subsequent Event
Class of Stock [Line Items]
Cash dividends declared (dollars per share)	$ 0.14
Cash dividends declared	$ 35,000,000
Increase in cash dividends declared (dollars per share)	$ 0.04