Stockholders' Equity (Share Repurchases) (Details) - USD ($)	3 Months Ended	9 Months Ended
	Apr. 30, 2017	Jul. 31, 2017	Jul. 31, 2016	Mar. 21, 2017	Dec. 15, 2011
Equity [Abstract]
Share Repurchase Program, maximum amount authorized				$ 1,000,000,000.0	$ 500,000,000.0
Number of common stock repurchased, shares	150,000	0	0
Treasury Stock, Value, Acquired, Cost Method	$ 29,500,000
Accelerated Share Repurchases, Final Price Paid Per Share	$ 196.82
Share Repurchase Program, remaining authorized amount		$ 589,000,000