Stockholders' Equity (Stock Options Vested, Or Expected to Vest and Are Exercisable) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016
Stock-Based Compensation
Options outstanding, Number of options	5,280	5,331	4,944
Options outstanding, Weighted-Average Exercise Price	$ 39.47	$ 39.43	$ 35.35
Options outstanding, Weighted-Average Remaining Life in Years	6 years 1 month 6 days
Options outstanding, Aggregate Intrinsic Value	$ 148,468
Options vested and exercisable, Number of options	3,216
Options vested and exercisable, Weighted-Average Exercise Price Per Share	$ 32.81
Options vested and exercisable, Weighted-Average Remaining Life in Years	4 years 8 months 12 days
Options vested and exercisable, Aggregate Intrinsic Value	$ 111,835
Options vested and expected to vest, Number of options	5,192
Options vested and expected to vest, Weighted-Average Exercise Price Per Share	$ 39.25
Options vested and to expected vest, Weighted-Average Remaining Life in Years	6 years 1 month 6 days
Options vested and expected to vest, Aggregate Intrinsic Value	$ 147,107