Shareholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions	1 Months Ended					3 Months Ended
	Oct. 31, 2017	Sep. 30, 2017	Jul. 31, 2017	Apr. 30, 2017	Oct. 31, 2016	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Apr. 28, 2017
Class of Stock [Line Items]
Dividend declared (in dollars per share)		$ 0.6					$ 0.48	$ 0.48	$ 0.48	$ 0.48	$ 0.375	$ 0.375	$ 0.375
Common stock, dividends, cash paid (in dollars per share)										$ 0.375		0.375
Common stock, dividends, cash paid for dividends declared in prior period (in dollars per share)			$ 0.48	$ 0.48	$ 0.48			$ 0.48				$ 0.375
Common stock repurchase program, authorized amount														$ 500,000,000
Shares repurchased (shares)						1.0
Treasury stock value						$ 125,000,000
Remaining stock available for repurchase (shares)		$ 375,000,000				$ 375,000,000
Subsequent Event
Class of Stock [Line Items]
Common stock, dividends, cash paid for dividends declared in prior period (in dollars per share)	$ 0