Stockholders' Equity (Stock Options Vested, Or Expected to Vest and Are Exercisable) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Stock-Based Compensation
Options outstanding, Number of options	5,236	4,944
Options outstanding, Weighted-Average Exercise Price	$ 39.58	$ 35.35
Options outstanding, Weighted-Average Remaining Life in Years	5 years 10 months 24 days
Options outstanding, Aggregate Intrinsic Value	$ 199,098
Options vested and exercisable, Number of options	3,164
Options vested and exercisable, Weighted-Average Exercise Price Per Share	$ 32.80
Options vested and exercisable, Weighted-Average Remaining Life in Years	4 years 6 months
Options vested and exercisable, Aggregate Intrinsic Value	$ 141,785
Options vested and expected to vest, Number of options	5,164
Options vested and expected to vest, Weighted-Average Exercise Price Per Share	$ 39.39
Options vested and to expected vest, Weighted-Average Remaining Life in Years	5 years 10 months 24 days
Options vested and expected to vest, Aggregate Intrinsic Value	$ 197,348