Stockholders' Equity (Share Repurchases) (Details) - USD ($)	9 Months Ended	12 Months Ended
	Jul. 31, 2018	Oct. 31, 2017	Mar. 31, 2017
Equity [Abstract]
Share Repurchase Program, increase amount			$ 500,000,000.0
Share Repurchase Program, maximum amount authorized			$ 1,000,000,000.0
Number of common stock repurchased, shares	0	258,000
Common stock repurchased, value		$ 55,000,000
Share Repurchase Program, remaining authorized amount	$ 563,500,000